This summary highlights selected information from this proxy statement/prospectus related to the Business Combination and may not contain all of the information that is important to you. To understand the Business Combination more fully and for a more complete description of the legal terms of the Business Combination, you should carefully read and consider this entire proxy statement/prospectus and the annexes to this proxy statement/prospectus, including the Merger Agreement, along with all of the documents to which we refer in this proxy statement/prospectus, as they contain important information about, among other things, the Business Combination and how it affects you. The Merger Agreement is attached as Annex A to this proxy statement/prospectus. You should carefully read and consider the entire Merger Agreement, which is the legal document that governs the Business Combination.

Parties to the Business Combination (page [•])

ATII

ATII is a blank check company incorporated on June 7, 2024, as a Cayman Islands exempted company to effect a merger, share exchange, asset acquisition, share purchase, reorganization or similar business combination with one or more businesses during the Completion Window.

The ATII Public Units, ATII Public Shares and ATII Public Warrants are currently traded on Nasdaq under the ticker symbols “ATIIU,” “ATII” and “ATIIW,” respectively.

ATII’s principal executive office is located at 2093 Philadelphia Pike #1968, Claymont, DE 19703. Its telephone number is (725) 312-2430. ATII’s corporate website address is www.archimedesspac2.com. ATII’s website and the information contained on, or that can be accessed through, the website is not deemed to be incorporated by reference in, and is not considered part of, this proxy statement/prospectus.

Forge Nano

Forge Nano is a leading technology company pioneering domestic battery and semiconductor innovations. Forge Nano develops and commercializes nanocoating and ALD technologies, a process that provides perfectly conformal, atom-thin coatings on surfaces, wafers and powders for battery cells, semiconductor devices and other advanced hardware applications.

Forge Nano was incorporated in Delaware on July 14, 2017 pursuant to the DGCL. Forge Nano’ principal executive office is located at 12300 Grant St. #100, Thornton, CO 80241 and its telephone number is (720) 259-8579. Forge Nano’ corporate website address www.forgenano.com. Forge Nano’s website and the information contained on, or that can be accessed through, the website is not deemed to be incorporated by reference in, and is not considered part of, this proxy statement/prospectus.

Pubco

Pubco is a wholly-owned subsidiary of ATII formed solely for the purpose of effecting the Domestication Merger and the Business Combination. Pursuant to the Merger Agreement, at least one day prior to the First Effective Time and at the Domestication Merger Effective Time, ATII and Pubco will consummate the Domestication Merger, with Pubco as the surviving corporation, as more fully described elsewhere in this proxy statement/prospectus. Pubco was incorporated in Delaware on December 4, 2025. Pubco owns no material assets and does not operate any business. Pubco’s principal executive office is located at 2093 Philadelphia Pike #1968, Claymont, DE 19703. Its telephone number is (725) 312-2430.

Merger Sub I

Merger Sub I is a wholly-owned subsidiary of ATII formed solely for the purpose of effecting the First Company Merger. Pursuant to the Merger Agreement, at least one day following the Domestication Merger Effective Time and at the First Effective Time, Merger Sub I will merge with and into Forge Nano, with Forge Nano as the Initial Surviving Corporation and a wholly-owned subsidiary of Pubco. Merger Sub I was incorporated in Delaware on December 4, 2025. Merger Sub I owns no material assets and does not operate any business. Merger Sub I’s principal executive office is located at 2093 Philadelphia Pike #1968, Claymont, DE 19703. Its telephone number is (725) 312-2430.

Merger Sub II

Merger Sub II is a wholly-owned subsidiary of ATII formed solely for the purpose of effecting the Second Company Merger. Immediately following the First Effective Time and at the Second Effective Time, the Initial Surviving Corporation will merge with and into Merger Sub II, with Merger Sub II as the surviving entity and a wholly-owned subsidiary of Pubco. Merger Sub II was formed in Delaware on December 11, 2025. Merger Sub II owns no material assets and does not operate any business. Merger Sub II’s principal executive office is located at 2093 Philadelphia Pike #1968, Claymont, DE 19703. Its telephone number is (725) 312-2430.

Organizational Structure

The following diagram depicts a simplified version of the current organizational structures of ATII and Forge Nano prior to, and after, the consummation of the Proposed Transaction, taking into account various assumptions, as further described below under the sections of this proxy statement/prospectus entitled “Proposal No. 1 – The Business Combination Proposal – Ownership of Pubco After the Closing” and “Unaudited Pro Forma Condensed Combined Financial Information.”

All of the relative percentages below are for illustrative purposes only and are based on certain assumptions as described in the section entitled “Unaudited Pro Forma Condensed Combined Financial Information.” For more information, including the ownership percentages in the No Additional Redemptions Scenario and the effect of certain dilutive securities, see the section entitled “Proposal No. 1 – The Business Combination Proposal – Ownership of Pubco After the Closing” and as described under the presentation described as “Assuming No Additional Redemptions Scenario” in the section entitled “Unaudited Pro Forma Condensed Combined Financial Information.

Simplified Pre-Business Combination Structures

Simplified Post-Business Combination Structures⁽¹⁾

shares of Pubco Common Stock underlying the Pubco Ascent Warrants, (e) the 15,000,000 shares of Pubco Common Stock underlying the PIPE Warrants, (f) the up to 10,000,000 shares of Pubco Common Stock underlying the Reset PIPE Warrants, (g) the 5,000,000 shares of Pubco Common Stock underlying the Additional PIPE Warrants and (h) the 90,000,000 Earn-Out Shares in the No Additional Redemptions Scenario and the Maximum Redemptions Scenario, respectively.

The Proposals to be Submitted at the Extraordinary General Meeting

Proposal No. 1 — The Business Combination Proposal

As discussed in this proxy statement/prospectus, ATII will ask the holders of ATII Ordinary Shares to approve and adopt, by Ordinary Resolution of the holders of ATII Ordinary Shares, the Business Combination Proposal. The ATII Board has unanimously approved the Business Combination Proposal and recommended its approval to the holders of ATII Ordinary Shares at the extraordinary general meeting.

The Business Combination (page [    ])

Domestication Merger

On the terms and subject to the conditions of the Merger Agreement, and in accordance with the Companies Act and the DGCL, at least one (1) day prior to the First Effective Time, and at the Domestication Merger Effective Time, ATII will re-domicile and become a Delaware corporation by merging with Pubco, following which the separate corporate existence of ATII will cease and Pubco will continue its corporate existence as the surviving corporation under the DGCL. At the Domestication Merger Effective Time, Pubco, as the surviving corporation under the DGCL pursuant to the Domestication Merger, will no longer be subject to the provisions of the Companies Act. At the Domestication Merger Effective Time, Pubco will adopt Delaware Organizational Documents, which will provide, among other things, that the name of Pubco will be changed to “Forge Nano Holdings Inc.”

If the Domestication Merger Proposal is approved, ATII and Pubco will consummate the Domestication Merger by executing and filing (1) a Plan of Merger, appended to the accompanying proxy statement/prospectus as Exhibit 3.4 (and any other documents required by the Companies Act) with the Cayman Registrar pursuant to Sections 233 and 237 of the Companies Act and such other filings or recordings in accordance with the Companies Act in connection with the consummation of the Domestication Merger and (2) a certificate of merger with the Secretary of State of the State of Delaware and such other filings or recordings in accordance with the relevant provisions of the DGCL in connection with the consummation of the Domestication Merger. The Domestication Merger will become effective at such time when the Plan of Merger is registered by the Cayman Registrar and when the certificate of merger is filed with the Secretary of State of the State of Delaware, or such later time as may be specified in the Plan of Merger and certificate of merger in accordance with the Companies Act and DGCL, respectively.

Immediately prior to the Domestication Merger Effective Time, each then issued and outstanding ATII Unit will separate and convert automatically into one ATII Ordinary Share and one-half of one ATII Warrant, and all ATII Units will cease to be outstanding and will cease to exist. At the Domestication Merger Effective Time, (1) each then issued and outstanding ATII Ordinary Share (which, for the avoidance of doubt, includes ATII Ordinary Shares held as a result of the separation of the ATII Units, but does not include any ATII Public Shares subject to Redemption) will be cancelled in exchange for the right to receive one share of Pubco Common Stock, (2) each ATII Warrant that is outstanding and unexercised will convert automatically into one Pubco SPAC Warrant pursuant to the terms of the ATII Warrant Agreement and (3) each ATII Public Share subject to Redemption issued and outstanding immediately prior to the Domestication Merger Effective Time will automatically be cancelled and cease to exist and will thereafter represent only the right of such ATII Public Shareholder to be paid a pro rata share of the Redemption Price in accordance with the Current Charter.

For more information, please see the section of this proxy statement entitled “Proposal No. 2 – The Domestication Merger Proposal.”

First Company Merger

On the terms and subject to the conditions set forth in the Merger Agreement, and in accordance with the DGCL, at least one (1) day following the Domestication Merger Effective Time, and at the First Effective Time, Merger Sub I will merge with and into Forge Nano, following which the separate corporate existence of Merger Sub I will cease and Forge Nano will continue its corporate existence as the Initial Surviving Corporation under the DGCL. As a result of the First Company Merger, Forge Nano will become a wholly-owned subsidiary of Pubco.

If the Business Combination Proposal is approved, ATII and Forge Nano will cause the First Company Merger to be consummated by executing and filing a certificate of merger with the Secretary of State of the State of Delaware and make such other filings or recordings, in each case, in accordance with the relevant provisions of the DGCL in connection with the consummation of the First Company Merger. The First Company Merger will become effective at such time as the certificate of merger with respect to the First Company Merger has been fully filed with the Secretary of State of the State of Delaware or at such later date or time as may be agreed by the parties in writing and specified in the certificate of merger in accordance with the DGCL.

Merger Consideration

Forge Nano Stock; Forge Nano Convertible Securities

At the First Effective Time: (i) each share of each class of Forge Nano Preferred Stock that is issued and outstanding immediately prior to the First Effective Time shall be converted into shares of Forge Nano Common Stock pursuant to Forge Nano’s organizational documents as in effect immediately prior to the First Effective Time; (ii) each share of Forge Nano Common Stock that is issued and outstanding immediately prior to the First Effective Time (including shares of Forge Nano Common Stock issued upon conversion of the shares of Forge Nano Preferred Stock, but not including treasury shares which will be canceled immediately prior to the First Effective Time) will be cancelled and automatically converted into the right to receive, without interest, the Applicable Per Share Merger Consideration; (iii) each Forge Nano Warrant that is issued and outstanding and unexpired immediately prior to the First Effective Time will be assumed by Pubco and become a corresponding Pubco Forge Nano Warrant, subject to the same terms and conditions (including vesting and exercisability) as were applicable to the corresponding Forge Nano Warrant immediately prior to the First Effective Time; and (iv) each Forge Nano Ascent Option that is issued and outstanding and unexpired immediately prior to the First Effective Time will be cancelled and converted into one Pubco Ascent Warrant pursuant to the Pubco Ascent Warrant Agreement, substantially in the form attached to the Merger Agreement.

Earn-Out

Pursuant to the terms of the Merger Agreement, and subject to the terms and conditions set forth therein, the Forge Nano Stockholders who receive Closing Payment Shares and the holders of Pubco Convertible Securities issued in exchange for Forge Nano Convertible Securities, if any, will be entitled to receive, a proportional amount of up to an aggregate of 90,000,000 Earn-Out Shares, issuable upon achievement of certain milestones during the Earn-Out Period. The Earn-Out Shares will be issued at or prior to the Closing to the Escrow Agent and will be disbursed therefrom upon achievement of the applicable milestones as follows:

The milestones applicable to the Earn-Out Shares operate on a cumulative basis, such that if a higher milestone is achieved, the lower milestones are deemed achieved as well and the Earn-Out Shares attributable to such achieved milestone and each lower

milestone will be disbursed. The Earn-Out Shares attributable to holders of Pubco Convertible Securities issued in exchange for Forge Nano Convertible Securities, if any, pursuant to the Merger Agreement will only be disbursed by the Escrow Agent if an applicable milestone is achieved upon the exercise, conversion or settlement thereof in accordance with their terms.

Ownership of Applicable Per Share Merger Consideration (page [•])

All shares of Pubco Common Stock and Earn-Out Shares to be issued to the Forge Nano Stockholders who receive Closing Payment Shares and holders of Pubco Convertible Securities issued in exchange for Forge Nano Convertible Securities in accordance with, and subject to the terms and conditions of, the Merger Agreement, will be issued by Pubco fully paid and non-assessable, free and clear of all liens, other than restrictions arising from applicable securities laws or from any Lock-Up Agreement between Pubco and the Forge Nano Lock-Up Holders, who are expected to collectively own approximately 53.15% of Pubco Common Stock at Closing assuming the No Additional Redemptions Scenario, and approximately 63.03% of Pubco Common Stock at Closing assuming the Maximum Redemptions Scenario, pursuant to which the Forge Nano Lock-Up Holders are subject to transfer restrictions (subject to certain exceptions). For more information about the Merger Agreement and the Business Combination, see the section titled “Proposal No. 1 – The Business Combination Proposal.

Treatment of Forge Nano Equity Awards (page [●])

At the First Effective Time, each Forge Nano Option that is issued and outstanding and unexpired immediately prior to the First Effective Time will be converted into one Pubco Option on substantially the same terms and conditions, including with respect to vesting and termination-related provisions (as applicable, except that such Pubco Options will relate to the number of whole shares of Pubco Common Stock (rounded down to the nearest whole share) equal to the product (rounded down to the nearest whole number) of (a) the number of shares of Forge Nano Common Stock subject to such Forge Nano Option immediately prior to the First Effective Time and (b) the quotient of (1) the Applicable Per Share Merger Consideration divided by (ii) the Equity Award Conversion Amount (as defined in the Merger Agreement), with an exercise price per Pubco Option (rounded up to the nearest whole cent) equal to the quotient obtained by dividing (x) the exercise price per Forge Nano Option by (ii) the Equity Award Conversion Amount.

Second Company Merger

Pursuant to the Merger Agreement, and subject to the terms and conditions set forth therein, immediately following the First Effective Time, the Initial Surviving Corporation will merge with and into Merger Sub II, with Merger Sub II surviving as the Surviving Company and Pubco acquiring one membership interest in Surviving Company and such membership interest will constitute the only outstanding equity of the Surviving Company.

For more information, please see the section of this proxy statement entitled “Proposal No. 1 – The Business Combination Proposal – Merger Consideration.”

Material U.S. Federal Income Tax Considerations of the Business Combination (page 158)

For a description of certain material U.S. federal income tax considerations of the Business Combination and the exercise of Redemption Rights and the ownership and disposition of shares of Pubco Common Stock and/or Pubco Warrants in connection with the Business Combination, see the section titled “Material U.S. Federal Income Tax Considerations.”

Appraisal Rights (page 106)

Appraisal rights are not available to holders of ATII Ordinary Shares in connection with the Business Combination.

Regulatory Approvals Required for the Business Combination (page [•])

U.S. Regulatory Clearance

Under the Merger Agreement, the Business Combination cannot be consummated until the waiting period applicable to the Business Combination under the HSR Act have expired or been terminated.

The Business Combination is not subject to any federal or state regulatory requirements or approvals, except for filings with the State of Delaware necessary to effectuate the Business Combination at the Closing.

For more information, please see the section of this proxy statement/prospectus entitled “Proposal No. 1 – The Business Combination Proposal – Regulatory Approvals Required for the Business Combination.

Conditions to Closing (page 122)

The obligations of the parties to consummate the Business Combination are subject to the satisfaction or waiver of customary conditions, including (among other conditions) the following:

For more information, please see the section of this proxy statement/prospectus entitled “Proposal No. 1 – The Business Combination Proposal – Conditions to the Closing of the Business Combination.”

Vote Required for Approval

The approval and adoption of the Business Combination Proposal requires an Ordinary Resolution of the holders of ATII Ordinary Shares under the Companies Act and the Current Charter, being a resolution passed by the affirmative vote of a simple majority of the votes cast by holders of the ATII Ordinary Shares as, being entitled to do so, vote in person or, where proxies are allowed, by proxy at the extraordinary general meeting (assuming presence of a quorum).

Each Condition Precedent Proposal is conditioned upon the approval of the other Condition Precedent Proposals. Therefore, if all Condition Precedent Proposals are not approved, none of the Condition Precedent Proposals will have any effect, even if certain Condition Precedent Proposals are approved by holders of ATII Ordinary Shares.

The Sponsor, which includes among its members each of the ATII Directors and the officers of ATII, and BTIG have the right to vote, collectively, 6,590,000 ATII Ordinary Shares. As a result, 8,205,001 additional votes of holders of ATII Ordinary Shares will be required to approve and adopt, by Ordinary Resolution of the holders of ATII Ordinary Shares, the Business Combination Proposal, the Director Election Proposal, the Stock Issuance Proposal, the Advisory Organizational Documents Proposals, the Equity Incentive Plan Proposal and, if presented, the Adjournment Proposal, while 13,136,667 additional votes of holders of ATII Ordinary Shares will

be required to approve and adopt, by Special Resolution of the holders of ATII Ordinary Shares, the Domestication Merger Proposal and the Organizational Documents Proposal.

Date, Time and Place of the Extraordinary General Meeting

The extraordinary general meeting to consider and vote on the proposal to adopt the Merger Agreement will be held at           Eastern Time on             , 2026 and will be a virtual meeting conducted via live webcast at           (the “extraordinary general meeting website”). For the purposes of Cayman Islands law and the Current Charter, the physical location of the extraordinary general meeting will be at the offices of ATII at.

Registering for the Extraordinary General Meeting

Any holder of ATII Ordinary Shares wishing to attend the extraordinary general meeting virtually must pre-register for the extraordinary general meeting at         by          Eastern Time on            , 2026. For purposes of attendance at the extraordinary general meeting, all references in this proxy statement to “present” shall mean virtually present at the extraordinary general meeting. To register for the extraordinary general meeting, please follow these instructions as applicable to the nature of your ownership of ATII Ordinary Shares:

Voting Power; Record Date

Only holders of ATII Ordinary Shares at the close of business on the Record Date are entitled to notice of the extraordinary general meeting and to vote at the extraordinary general meeting pursuant to the Companies Act and the Current Charter. A list of holders of ATII Ordinary Shares entitled to vote at the extraordinary general meeting will be available at our principal executive offices located at 2093 Philadelphia Pike #1968, Claymont, DE 19703, during regular business hours for a period of no less than ten days prior to the extraordinary general meeting, as well as electronically at the extraordinary general meeting website. As of        , 2026, which is the Record Date for the extraordinary general meeting, there were 29,590,000 ATII Ordinary Shares outstanding, of which 23,000,000 were ATII Public Shares held by persons other than the Insiders. Holders of ATII Ordinary Shares will be entitled to one vote for each ATII Ordinary Share owned at the close of business on the Record Date.

If you hold your ATII Ordinary Share in “street name”, you should instruct your bank, broker or other nominee how to vote your ATII Ordinary Shares at the extraordinary general meeting in accordance with the voting instruction form that you will receive from your bank, broker or other nominee. Your bank, broker or other nominee cannot vote on any of the proposals, including the Business Combination Proposal, without your instructions. ATII Warrants do not have voting rights.

Abstentions and Broker Non-Votes

If your ATII Ordinary Shares are held in a stock brokerage account or by a bank or other nominee, you are considered the “beneficial holder” of the ATII Ordinary Shares held for you in what is known as “street name.” If this is the case, this proxy statement/prospectus may have been forwarded to you by your brokerage firm, bank or other nominee, or its agent, and you may need to obtain a proxy form from the institution that holds your ATII Ordinary Shares and follow the instructions included on that form

regarding how to instruct your broker, bank or nominee as to how to vote your ATII Ordinary Shares. Under the rules of various national and regional securities exchanges, your broker, bank, or nominee cannot vote your ATII Ordinary Shares with respect to non-discretionary matters unless you provide instructions on how to vote in accordance with the information and procedures provided to you by your broker, bank, or nominee. We believe all the proposals presented to the holders of ATII Ordinary Shares will be considered non-discretionary and therefore your broker, bank, or nominee cannot vote your ATII Ordinary Shares without your instruction. Your bank, broker, or other nominee can vote your ATII Ordinary Shares only if you provide instructions on how to vote. As the beneficial holder of the ATII Ordinary Shares, you have the right to direct your broker, bank or other nominee as to how to vote your ATII Ordinary Shares and you should instruct your broker to vote your ATII Ordinary Shares in accordance with directions you provide. If you do not provide voting instructions to your broker on a particular proposal on which your broker does not have discretionary authority to vote, your ATII Ordinary Shares will not be voted on that proposal. This is called a “broker non-vote.”

Abstentions and broker non-votes, while considered present for the purposes of establishing a quorum at the extraordinary general meeting, will not count as votes cast at the extraordinary general meeting, and otherwise will have no effect on a particular proposal under the Companies Act and the Current Charter.

Quorum

The presence, in person or represented by proxy, of the holders of a majority of the ATII Ordinary Shares entitled to vote on the Record Date will constitute a quorum at the extraordinary general meeting pursuant to the Companies Act and the Current Charter. As of the Record Date, the presence, in person or represented by proxy, of the holders of at least 14,795,001 ATII Ordinary Shares would be required to achieve a quorum at the extraordinary general meeting. Because the Sponsor and BTIG have the right to vote, collectively, 6,590,000 ATII Ordinary Shares and will attend the extraordinary general meeting in connection with the Proposed Transaction, the presence at the extraordinary general meeting of additional holders of 8,205,001 ATII Ordinary Shares would be required to achieve a quorum at the extraordinary general meeting. Abstentions and broker non-votes, while considered present for the purposes of establishing a quorum at the extraordinary general meeting, will not count as a vote cast at the extraordinary general meeting and otherwise will have no effect on a particular proposal under the Companies Act and the Current Charter. In the event that quorum is not present at the extraordinary general meeting, it is expected that the extraordinary general meeting will be adjourned to solicit additional proxies.

Recommendation of ATII Board

The ATII Board, after considering the factors more fully described in the enclosed proxy statement/prospectus, has unanimously: (i) determined that the Merger Agreement and the transactions contemplated thereby, including the Business Combination, are fair to and in the best interests of ATII and the holders of ATII Ordinary Shares, (ii) approved and declared advisable the Merger Agreement and the transactions contemplated thereby, including the execution, delivery and performance of the Merger Agreement, (iii) directed that the adoption of the Merger Agreement be submitted to a vote of the holders of ATII Ordinary Shares at the extraordinary general meeting and (iv) resolved to recommend the adoption of the Merger Agreement and the approval of the Business Combination Proposal by the holders of ATII Ordinary Shares at the extraordinary general meeting.

ATII Board’s Reasons for the Approval of the Business Combination and the Transaction Contemplated Thereby

The ATII Directors and officers of ATII have substantial experience in evaluating the operating and financial merits of companies from a wide range of industries and concluded that their experience and background enabled such ATII Directors and officers of ATII to make the necessary analyses and determinations regarding the Business Combination. After careful consideration of the terms and conditions of the Merger Agreement, the ATII Board has determined that the Business Combination and the transactions contemplated thereby are fair to and in the best interests of ATII and the holders of ATII Ordinary Shares because the ATII Board believes that Forge Nano is a company with strong revenue growth potential. Forge Nano has been operating for some time and the ATII Board believes that they have demonstrated a good return on investment capital for their client base in the semiconductor space. In reaching its decision with respect to the Business Combination and the transactions contemplated thereby, the ATII Board also reviewed various industry and financial data and the due diligence and evaluation materials provided by Forge Nano, demonstrating that Forge Nano has a business plan dedicated to both near-term cash flow as well as long-term growth. For additional information regarding the positive and negative factors the ATII Board considered in evaluating the Business Combination, see the section entitled “Proposal No. 1 – The Business Combination Proposal — ATII Board Reasons for the Approval of the Business Combination” on page [        ].

Interests of the ATII Directors and officers of ATII in the Business Combination

When you consider the recommendation of the ATII Board in favor of approval of the Business Combination Proposal, you should keep in mind that the Sponsor, the ATII Directors and the officers of ATII have interests in such proposal that are different from, or in addition to, those of the holders of ATII Ordinary Shares generally. See “Proposal No. 1 – The Business Combination Proposal — Certain Interests of ATII’s Directors and Officers and Others in the Business Combination.”

The existence of financial and personal interests of one or more of ATII Director may result in a conflict of interest on the part of such ATII Director(s) between what he, she or they may believe is in the best interests of ATII and the holders of ATII Ordinary Shares and what he, she or they may believe is best for himself, herself or themselves in determining to recommend that holders of ATII Ordinary Shares vote for the proposals. In addition, ATII’s officers have interests in the Business Combination that may conflict with your interests as a holder of ATII Ordinary Shares.

The personal and financial interests of the Sponsor, the ATII Directors and officers of ATII may have influenced their motivation in identifying and selecting Forge Nano as a business combination target, completing an initial business combination with Forge Nano and influencing the operation of the business following the Closing. In considering the recommendations of the ATII Board to vote for the proposals, holders of ATII Ordinary Shares should consider these interests.

Termination of the Merger Agreement

The Merger Agreement may be terminated and/or the Business Combination may be abandoned by ATII or Forge Nano under certain circumstances at any time prior to the Closing, including, among others, (i) by mutual agreement; (ii) the imposition of a final and non-appealable Order or other Action issued by a Governmental Authority of competent jurisdiction that permanently prevents or prohibits consummation of the Business Combination; provided, however, that such right to terminate shall not be available to ATII or Forge Nano if the failure by such party or its affiliates to comply with any provision of the Merger Agreement has been a substantial cause of, or substantially resulted in, such action by such Governmental Authority; (iii) certain uncured breaches of the Merger Agreement by the other party; (iv) if (x) the Business Combination has not been consummated by on or before January 20, 2027 (the “Outside Date”) and (y) the breach or violation of any representation, warranty or covenant under the Merger Agreement by the party seeking to terminate the Merger Agreement is not the cause of, or has not resulted in, the failure of the Closing to occur by the Outside Date; and (v) if the holders of ATII Ordinary Shares fail to adopt the Merger Agreement at the extraordinary general meeting (or any adjournment or postponement thereof).

Comparison of Corporate Governance and Shareholder Rights (page 249)

For a summary of the material differences among the rights of holders of Pubco Common Stock and holders of ATII Ordinary Shares, see the section titled “Comparison of Corporate Governance and Shareholder Rights.”

Board of Directors of Pubco Following the Business Combination (page [●])

Following the First Effective Time, subject to the Director Election Proposal, it is expected that the board of directors of Pubco will consist of six (6) directors (which will be divided into three classes, designated Class I, Class II and Class III, each consisting of two directors), the members of which are currently expected to be Paul Lichty, Michael Danner, David Goggins, Millicent Pitts-DiCicco, Jimmy Smith, and Ben Landen. At the Closing, these six (6) directors will comprise the Pubco Board.

Information about the current ATII directors and executive officers can be found in the section titled “Where You Can Find More Information.”

Effect on ATII If the Business Combination is Not Consummated

If the Merger Agreement is not adopted by the holders of ATII Ordinary Shares, or if the Business Combination is not consummated for any other reason, the holders of ATII Ordinary Shares will not be entitled to, nor will they receive, any payment for their respective ATII Ordinary Shares pursuant to the Merger Agreement.

Other Agreements (page [•])

The following agreements were entered into or will be entered into in connection with the Business Combination, the Merger Agreement and the other transactions contemplated thereby:

Purchaser Support Agreement

Concurrently with their entry into the Merger Agreement, ATII and Forge Nano entered into the Purchaser Support Agreement with the Sponsor, pursuant to which the Sponsor agreed (i) to vote all of its ATII Ordinary Shares held by the Sponsor in favor of the approval and adoption of the Merger Agreement and the Business Combination, (ii) to not redeem, sell or tender, during the term of the Purchaser Support Agreement, any ATII Ordinary Shares owned by the Sponsor in connection with the Business Combination and (iii) to not transfer any ATII Ordinary Shares held by the Sponsor in accordance with the lock-up provisions set forth in ATII’s final prospectus filed with the SEC on February 11, 2025.

Pursuant to the Purchaser Support Agreement, and subject to the terms and conditions set forth therein, the Sponsor also agreed to contribute up to 3,300,000 ATII Ordinary Shares, together with all shares of Pubco Common Stock issued upon conversion thereof, including any securities paid as dividends or distributions with respect to or into which such shares are exchanged or converted to secure one or more financing transactions in connection with the Business Combination. To the extent the parties to the PIPE Subscription Agreement (as described below) fund any Financing Transaction of at least $100 million, the Sponsor will transfer to such party 3,000,000 ATII Ordinary Shares to secure such Financing Transaction; and the remaining 300,000 ATII Ordinary Shares will be transferred to investors to secure other Financing Transactions to the extent such Financing Transactions are funded by such investors. Any such ATII Ordinary Shares not used to secure Financing Transactions will be retained by the Sponsor.

The Purchaser Support Agreement is filed as Annex C to this proxy statement/prospectus, and the foregoing description thereof is qualified in its entirety by reference to the full text of the Purchaser Support Agreement and the terms of which are incorporated by reference herein.

For additional information, see section titled “Proposal No. 1 – The Business Combination Proposal – Other Agreements – Purchaser Support Agreement.”

Lock-Up Agreement

In connection with their entry into the Merger Agreement, ATII and Forge Nano entered into Lock-Up Agreements with each of the Forge Nano Lock-Up Holders, who are expected to collectively own approximately 53.15% of Pubco Common Stock at Closing assuming the No Additional Redemptions Scenario, and approximately 63.03% of Pubco Common Stock assuming the Maximum Redemptions Scenario. Pursuant to the Lock-Up Agreement, each Forge Nano Lock-Up Holder agreed that each such holder will not, during the Lock-Up Period, directly or indirectly sell, exchange, assign, transfer (including by merger, conversion or operation of law), gift or otherwise dispose, any of the Lock-Up Shares, whether or not any transaction is to be settled by delivery of Lock-Up Shares or such other securities, in cash or otherwise, or make a public announcement of any intention to effect such a transfer.

The form of Lock—Up Agreement is filed as Annex D to this proxy statement/prospectus, and the foregoing description thereof is qualified in its entirety by reference to the full text of the Lock-Up Agreement and the terms of which are incorporated by reference herein.

Additionally, pursuant to the Insider Letter, the Sponsor and each Insider agreed to restrictions on transfer following the Closing Date with respect to Founder Shares, including a lock-up, subject to certain exceptions, in each case ending on the earlier of (a) six months following the Closing Date and (b) the date the last reported sale price of Pubco Common Stock equals or exceeds $12.00 per share (subject to adjustment) for any twenty trading days within any thirty- (30-) trading day period after the Closing Date.

For additional information, see the section titled “Proposal No. 1 – The Business Combination Proposal – Other Agreements – Lock-Up Agreement.”

A&R Registration Rights Agreement

The Insiders, the Significant Forge Nano Holders and the PIPE Investor will each enter into the A&R Registration Rights Agreement, to be delivered at or prior to the Closing, pursuant to which, among other things, Pubco will be obligated to file a registration statement on Form S-1 with the SEC as soon as practicable but no later than 30 calendar days following the Closing to register the resale of certain securities of Pubco held by the Subject Parties, and to use its commercially reasonable efforts to have such registration statement declared effective as soon as practicable after the filing thereof, but no later than the earlier of (i) 60 calendar days after its filing (or 90 calendar days after its filing if the SEC notifies Pubco that it will “review” such registration statement) and (ii) five business days after Pubco is notified by the SEC that such registration statement will not be “reviewed” or will not be subject to further review, subject to customary liquidated damages in the event Pubco is unable to meet the filing deadline. The

A&R Registration Rights Agreement will also provide the Subject Parties with “piggy-back” registration rights, subject to certain requirements and customary conditions. All expenses of registration under the A&R Registration Rights Agreement, including the legal fees of one firm of counsel chosen by stockholders participating in a registration, will be paid by the Company.

We estimate that the following securities of Pubco will be subject to registration rights immediately following the Closing: (1) the Insiders and BTIG will hold an aggregate of 3,359,000 shares of Pubco Common Stock, comprised of 2,750,000 Founder Shares held by Sponsor (assuming Sponsor transfers 3,000,000 ATII Ordinary Shares to the PIPE Investor and retains 300,000 ATII Ordinary Shares that are subject to transfer to secure additional financing in connection with the Business Combination pursuant to the Purchaser Support Agreement) and 530,000 ATII Private Units held by Sponsor and 310,000 ATII Private Units held by BTIG, for an aggregate of 420,000 Pubco SPAC Warrants held by the Insiders, (2) an aggregate of 72,086,674 shares of Pubco Common Stock held by Significant Forge Nano Holders, (3) the 9,186,673 shares of Pubco Common Stock underlying the Pubco Forge Nano Warrants and the 3,667,664 shares of Pubco Common Stock underlying the Pubco Ascent Warrants and (4) an aggregate of 13,000,000 shares of Pubco Common Stock (assuming Sponsor transfers 3,000,000 Sponsor Contribution Shares to the PIPE Investor) held by the PIPE Investor.

The registration rights granted in the A&R Registration Rights Agreement are subject to customary restrictions including blackout periods and, if a registration is underwritten, limitations on the number of shares to be included in the underwritten offering as reasonably advised by the managing underwriter or underwriters. The A&R Registration Rights Agreement also contains customary indemnification and contribution provisions.

The form of A&R Registration Rights Agreement is filed as Annex E to this proxy statement/prospectus, and the foregoing description thereof is qualified in its entirety by reference to the full text of the A&R Registration Rights Agreement and the terms of which are incorporated by reference herein.

PIPE Financing

In connection with the execution of the Merger Agreement, ATII, Pubco and Forge Nano entered the PIPE Subscription Agreement with the PIPE Investor, pursuant to which Pubco will, substantially concurrently with, and contingent upon, the consummation of the Business Combination, sell an aggregate of 10,000,000 shares of Pubco Common Stock and warrants to purchase an aggregate of 15,000,000 shares of Pubco Common Stock to the PIPE Investor, each with an exercise price of $10.00 (subject to adjustments as described below) for an aggregate purchase price of $100,000,000. Pursuant to the Purchaser Support Agreement, Sponsor has agreed to transfer 3,000,000 ATII Ordinary Shares of the PIPE Investor to the extent the PIPE Investor funds the PIPE Financing. In the event that on the 21st trading day following the six-month anniversary of Closing, the VWAP (as defined in the PIPE Warrant Certificate) of the Pubco Common Stock is less than the Exercise Price (as defined in the PIPE Warrant Certificate), Pubco will issue to the Investor the Reset PIPE Warrants entitling the PIPE Investor to purchase up to 10,000,000 shares of Pubco Common Stock, in an amount equal to (i) the product of (x) 5,000,000, multiplied by (y) the Exercise Price then in effect divided by the PIPE Reset Price minus (ii) 5,000,000. In addition, if, on the 24-month anniversary of the Closing Date, the PIPE Investor certifies in writing that the PIPE Investor beneficially owns 5,000,000 shares of Pubco Common Stock, Pubco will issue to the PIPE Investor the Additional PIPE Warrants entitling the PIPE Investor to purchase 5,000,000 shares of Pubco Common Stock.

The PIPE Closing is conditioned upon, among other things, (i) all conditions precedent to the closing of the Business Combination contemplated by the Merger Agreement shall have been satisfied or waived and the closing of the Business Combination shall be scheduled to occur concurrently with and on the same date as the PIPE Closing and (ii) the accuracy of all representations and warranties of ATII and Forge Nano in the PIPE Subscription Agreement (subject to certain bring-down standards).

PIPE Subscription Agreement

The PIPE Subscription Agreement contains representations, warranties and covenants of ATII, Forge Nano and the PIPE Investor that are customary for agreements of their nature. In addition, the PIPE Subscription Agreement contains the following provisions:

The PIPE Subscription Agreement is filed as Annex H to this proxy statement/prospectus, and the foregoing description thereof is qualified in its entirety by reference to the full text of the PIPE Subscription Agreement and the terms of which are incorporated by reference herein.

PIPE Warrants

The PIPE Warrants are exercisable for Pubco Common Stock at any time after the date of their issuance and expire five years after the date of their issuance. The exercise price per PIPE Warrant is $10.00, subject to adjustment as set forth in the Warrant Certificate and described below. The PIPE Warrants may be exercised on a cashless “net issuance” basis.

The PIPE Warrants are subject to a beneficial ownership limitation, at the election of the holder. If the election is made, Pubco will not effect any exercise of the PIPE Warrants, and a holder will not have the right to exercise any portion of the PIPE Warrants, to the extent that after giving effect to such issuance after exercise the holder (together with the holder’s affiliates, and anyone acting as a group together with the holder or any of the holder’s affiliates would beneficially own in excess of 4.9%, 9.9%, 19.9% (or such other amount as the holder may specify) of Pubco Common Stock.

The exercise price of the PIPE Warrants is subject to adjustment if Pubco (i) subdivides or combines (including by way of a reverse share split) the outstanding Pubco Common Stock, (ii) issues by reclassification of Pubco Common Stock into any capital shares of Pubco, (iii) issues any Pubco Common Stock credited as fully paid to shareholders by way of capitalization of profits or reserves, (iv) issues or sells pro rata to the record holders of Pubco Common Stock any rights, options or warrants entitling them to subscribe for or purchase Pubco Common Stock, or (v) declares or makes any dividend or other distribution of its assets (or rights to acquire its assets) to holders of Pubco Common Stock, by way of return of capital or otherwise.

The exercise price of the PIPE Warrants also is subject to a one-time adjustment based on the subsequent market price. If, on the 21^st trading day following the six-month anniversary of the Closing Date, the Measurement Price is less than the exercise price then in effect, then the Exercise Price then in effect shall be reduced to an amount equal to the greater of (i) the Measurement Price and (ii) (x) $7.28, if Forge Nano has secured at least $200 million in debt financing as of the Closing Date and (y) otherwise, $5.00.

In addition, the exercise price of the PIPE Warrants is subject to adjustment for subsequent equity issuances. If and whenever during the period commencing on the date of the PIPE Subscription Agreement and ending on the expiration date of the PIPE Warrants, Pubco issues or sells, or is deemed to have issued or sold, any Pubco Common Stock (subject to certain exceptions) for proceeds per share of Pubco Common Stock less than the exercise price then in effect (where the aggregate amount of proceeds received by Pubco, together with all prior issuances and sales (excluding any Exempt Issuance) conducted for the purpose of raising capital by Pubco on or after the date of the PIPE Subscription Agreements, exceeds $500,000), then immediately after such issuance, the exercise price then in effect shall be reduced to the amount of such proceeds per share of Pubco Common Stock. If there is any adjustment to the exercise price of the PIPE Warrants, the number of shares of Pubco Common Stock that may be purchased upon exercise of the PIPE Warrant shall also be increased or decreased proportionately so that after such adjustment the aggregate exercise price payable for the adjusted number of shares of Pubco Common Stock shall be the same as the aggregate exercise price in effect immediately prior to such adjustment.

At any time commencing on the two-year anniversary of the Closing Date, the PIPE Warrants may be redeemed, in whole or in part, at the Company’s option at the price of $0.01 per PIPE Warrant, provided that the closing price of the Pubco Common Stock equals or exceeds $35.00 per share (subject to adjustment in accordance with Section 3(a) of the Warrant Certificate), on each of twenty (20) trading days within any thirty (30) trading day period.

If a Fundamental Transaction (as defined in the Warrant Certificate) occurs, then, upon any subsequent exercise of a PIPE Warrant, the PIPE Investor will have the right to receive, for each share of Pubco Common Stock that would have been issuable upon such exercise immediately prior to the occurrence of such Fundamental Transaction, at the option of the PIPE Investor (without regard to the beneficial ownership limitation), the number of shares of the successor or acquiring corporation or of Pubco, if it is the surviving corporation, and any additional consideration receivable as a result of such Fundamental Transaction by a holder of the number of shares of Pubco Common Stock for which such PIPE Warrant is exercisable immediately prior to such Fundamental Transaction (without regard to the beneficial ownership limitation).

In connection with a Fundamental Transaction in which less than 70% of the consideration is payable in publicly listed common equity, the PIPE Investor has the option to require Pubco (or any successor entity) to repurchase its warrants for their Black Scholes Value (as defined in the Warrant Certificate) in cash.

The Warrant Certificate is filed as Annex I to this proxy statement/prospectus, and the foregoing description thereof is qualified in its entirety by reference to the full text of the Warrant Certificate and the terms of which are incorporated by reference herein.

See the section titled “Proposal No. 1 – The Business Combination Proposal – Other Agreements – PIPE Financing.”

Redemption Rights (page 55)

If you are an ATII Public Shareholder, you have the right to redeem your ATII Public Shares for a pro rata portion of the aggregate amount on deposit in the Trust Account, including interest earned on the Trust Account but not previously released to ATII to pay taxes, if any, which holds the net proceeds of the issuance of ATII Units in the IPO and concurrent private placement, upon the Closing.

Notwithstanding the foregoing, any ATII Public Shareholder, together with any affiliate of such ATII Public Shareholder or any other person with whom such ATII Public Shareholder is acting in concert or as a “group” (as defined in Section 13(d)(3) of the Exchange Act), will be restricted from redeeming its ATII Public Shares with respect to more than an aggregate of 15% of the ATII Public Shares then issued and outstanding without ATII’s prior consent. Accordingly, if any ATII Public Shareholder, alone or acting

in concert or as a “group”, seeks to redeem more than an aggregate of 15% of the ATII Public Shares then issued and outstanding, then any such shares in excess of that 15% limit would not be redeemed without ATII’s prior consent.

Holders of outstanding ATII Public Warrants do not have redemption rights with respect to such ATII Public Warrants in connection with the Business Combination.

You may exercise your Redemption Rights whether you vote your ATII Public Shares for or against, or whether you abstain from voting on, the Business Combination Proposal or any other proposal described in this proxy statement/prospectus. As a result, the Business Combination Proposal can be approved by ATII Public Shareholders who will redeem their ATII Public Shares in connection with the Proposed Transaction and will no longer be holders of ATII Public Shares, and the Business Combination may be consummated even though the funds available from the Trust Account and the number of ATII Public Shareholders are substantially reduced as a result of redemptions by ATII Public Shareholders in connection with the Business Combination. With fewer ATII Public Shares and ATII Public Shareholders, the trading market for ATII Public Shares may be less liquid than the market for ATII Public Shares prior to the Business Combination and Pubco may not be able to meet the listing standards of a national securities exchange, including Nasdaq. In addition, with fewer funds available from the Trust Account, the capital infusion from the Trust Account into Pubco’s and Forge Nano’s businesses will be reduced and the amount of working capital available to Pubco and Forge Nano following the Business Combination may be reduced. Your decision to exercise your Redemption Rights with respect to your ATII Public Shares will have no effect on the ATII Public Warrants you may also hold.

If you are a holder of ATII Public Shares and wish to exercise your Redemption Rights, you are required to tender your ATII Public Share certificates or deliver your shares to the Transfer Agent electronically using DTC’s DWAC (Deposit/Withdrawal at Custodian) System, at your option, in each case until the date that is two business days prior to the initially scheduled vote to approve the Business Combination Proposal at the extraordinary general meeting. Accordingly, you have until two days prior to the initial vote on the Business Combination Proposal at the extraordinary general meeting to tender your ATII Public Shares if you wish to exercise your Redemption Rights. Given the relatively short period in which to exercise your Redemption Rights, it is advisable for you to use electronic delivery of your ATII Public Shares. If you exercise your Redemption Right, your ATII Public Shares will be redeemed for a pro rata portion of the amount then in the Trust Account (which, for illustrative purposes, was approximately $239.9 million, or approximately $10.43 per share, as of December 31, 2025). Such amount, including any interest earned on the funds held in the Trust Account and not previously released to ATII to pay taxes, if any, will be paid promptly upon consummation of the Business Combination during the Completion Window. However, under Cayman Islands and Delaware law, the proceeds held in the Trust Account can be subject to claims that could take priority over those of the ATII Public Shareholders exercising Redemption Rights, regardless of whether such ATII Public Shareholders vote for or against the Business Combination Proposal. The per share distribution from the Trust Account in such a situation may be less than originally anticipated due to such claims. Your vote on any proposal other than the Business Combination Proposal will have no impact on the amount you will receive if you exercise your Redemption Rights.

The Transfer Agent may be contacted at the following address:

Odyssey Transfer and Trust Company

2155 Woodlane Drive, Suite 100

Woodbury, MN 55125

Attention: SPAC Redemption Team

Email:

Any request for redemption, once made by a holder of ATII Public Shares, may be withdrawn at any time up to two days prior to the vote on the Business Combination Proposal at the extraordinary general meeting. If you deliver your ATII Public Shares for redemption to the Transfer Agent and later decide, prior to the extraordinary general meeting, not to redeem your ATII Public Shares, you may request that the Transfer Agent return the shares electronically.

No demand will be effectuated unless the such ATII Public Shares have been delivered electronically to the Transfer Agent no later than two business day prior to the initially scheduled vote to approve the Business Combination Proposal at the extraordinary general meeting.

If an ATII Public Shareholder properly makes a request for redemption and the ATII Public Shares are delivered to the Transfer Agent no later than two business day prior to the initially scheduled vote to approve the Business Combination Proposal at the extraordinary general meeting, then, if the Business Combination is consummated during the Completion Window, ATII will redeem

such ATII Public Shares in exchange for a pro rata portion of funds deposited in the Trust Account. If you exercise your Redemption Rights, then you will be exchanging your ATII Public Shares for cash.

Proposal No. 2 — The Domestication Merger Proposal (page 131)

On the terms and subject to the conditions of the Merger Agreement, and in accordance with the Companies Act and the DGCL, at least one (1) day prior to the First Effective Time, and at the Domestication Merger Effective Time, ATII will re-domicile and become a Delaware corporation by merging with Pubco, following which the separate corporate existence of ATII will cease and Pubco will continue its corporate existence as the surviving corporation under the DGCL. At the Domestication Merger Effective Time, Pubco, as the surviving corporation under the DGCL pursuant to the Domestication Merger, will no longer be subject to the provisions of the Companies Act. At the Domestication Merger Effective Time, Pubco will adopt Delaware Organizational Documents, which will provide, among other things, that the name of Pubco will be changed to “Forge Nano Holdings Inc.”

If the Domestication Merger Proposal is approved, ATII and Pubco will consummate the Domestication Merger by executing and filing (1) a Plan of Merger, appended to the accompanying proxy statement/prospectus as Exhibit 3.4 (and any other documents required by the Companies Act) with the Cayman Registrar pursuant to Sections 233 and 237 of the Companies Act and such other filings or recordings in accordance with the Companies Act in connection with the consummation of the Domestication Merger and (2) a certificate of merger with the Secretary of State of the State of Delaware and such other filings or recordings in accordance with the relevant provisions of the DGCL in connection with the consummation of the Domestication Merger. The Domestication Merger will become effective at such time when the Plan of Merger is registered by the Cayman Registrar and when the certificate of merger is filed with the Secretary of State of the State of Delaware, or such later time as may be specified in the Plan of Merger and certificate of merger in accordance with the Companies Act and DGCL, respectively.

Immediately prior to the Domestication Merger Effective Time, each then issued and outstanding ATII Unit will separate and convert automatically into one ATII Ordinary Share and one-half of one ATII Warrant, and all ATII Units will cease to be outstanding and will cease to exist. At the Domestication Merger Effective Time, (1) each then issued and outstanding ATII Ordinary Share (which, for the avoidance of doubt, includes ATII Ordinary Shares held as a result of the separation of the ATII Units, but does not include any ATII Public Shares subject to Redemption) will be cancelled in exchange for the right to receive one share of Pubco Common Stock, (2) each ATII Warrant that is outstanding and unexercised will convert automatically into one Pubco SPAC Warrant pursuant to the terms of the ATII Warrant Agreement and (3) each ATII Public Share subject to Redemption issued and outstanding immediately prior to the Domestication Merger Effective Time will automatically be cancelled and cease to exist and will thereafter represent only the right of such ATII Public Shareholder to be paid a pro rata share of the Redemption Price in accordance with the Current Charter.

There are differences between Cayman Islands corporate law and Delaware corporate law, as well as between the Current Charter and the Proposed Organizational Documents. Accordingly, ATII encourages holders of ATII Ordinary Shares to carefully review the information in “Comparison of Corporate Governance and Shareholder Rights.”

For additional information, see the section titled “Proposal No. 2 – The Domestication Merger Proposal.”

Proposal No. 3 — The Director Election Proposal (page 136)

If each of the Business Combination Proposal and the Domestication Merger Proposal are approved, then ATII will ask the holders of ATII Ordinary Shares to approve and adopt, by Ordinary Resolution of the holders of ATII Ordinary Shares, the Director Election Proposal. The ATII Board has unanimously approved the Director Election Proposal and recommended its approval to the holders of ATII Ordinary Shares at the extraordinary general meeting.

The Director Election Proposal, if approved, will result in the election of six (6) directors to serve on the Pubco Board following the Closing Date as follows:

For additional information, please see the section titled “Proposal No. 3 – The Director Election Proposal.”

Proposal No. 4 — The Stock Issuance Proposal (page 139)

If each of the Business Combination Proposal, the Domestication Merger Proposal and the Director Election Proposal are approved, then ATII will ask the holders of ATII Ordinary Shares to consider and vote upon a proposal to approve, by Ordinary Resolution of the holders of ATII Ordinary Shares, for purposes of complying with the applicable provisions of the Nasdaq listing rules, the issuance of shares of Pubco Common Stock to be issued in the Business Combination, the Earn-Out Shares, the PIPE Subscribed Shares and the additional shares of Pubco Common Stock that will, upon Closing, be reserved for issuance pursuant to the 2026 Equity Plan, to the extent such issuances would require shareholder approval under Nasdaq listing rules. The ATII Board has unanimously approved the Stock Issuance Proposal and recommended its approval to the holders of ATII Ordinary Shares at the extraordinary general meeting.

Although Pubco Securities are not currently traded on Nasdaq, we have elected for Pubco to comply with all otherwise applicable Nasdaq rules upon the Domestication Merger Effective Time.

Pursuant to Nasdaq Listing Rule 5635(a), shareholder approval is required prior to the issuance of securities in connection with the acquisition of another company if, due to the present or potential issuance of common stock, including shares issued pursuant to an earnout provision or similar type of provision, or securities convertible into or exercisable for common stock, other than a public offering for cash and  have, or will have upon issuance, voting power equal to or in excess of 20% of the voting power outstanding before the issuance of common stock (or securities convertible into or exercisable for common stock); or  the number of shares of common stock to be issued is or will be equal to or in excess of 20% of the number of shares of common stock outstanding before the issuance of the stock or securities.

Under Nasdaq Listing Rule 5635(b), shareholder approval is required prior to an issuance of securities when the issuance or potential issuance will result in a change of control of the issuer.

Under Nasdaq Listing Rule 5635(d), shareholder approval is required for a transaction other than a public offering involving the sale, issuance or potential issuance by an issuer of common stock (or securities convertible into or exercisable for common stock) at a price that is less than the lower of (i) the closing price immediately preceding the signing of the binding agreement or (ii) the average closing price of the common stock for the five trading days immediately preceding the signing of the binding agreement, if the number of shares of common stock (or securities convertible into or exercisable for common stock) to be issued equals to 20% or more of the shares of common stock, or 20% or more of the voting power, outstanding before the issuance.

The aggregate shares of Pubco Common Stock that Pubco will and potentially will issue in connection with the Proposed Transaction will exceed 20% of both the voting power and the shares of Pubco Common Stock outstanding before such issuance and may result in a change of control under the applicable Nasdaq Listing Rules. Accordingly, ATII is seeking the approval of the holders of ATII Ordinary Shares for the issuance of shares of Pubco Common Stock in connection with the Proposed Transaction.

For additional information, please see the section titled “Proposal No. 4 – The Stock Issuance Proposal.”

Proposal No. 5 — The Organizational Documents Proposal (page 142)

If each of the Business Combination Proposal, the Domestication Merger Proposal, the Director Election Proposal and the Stock Issuance Proposal are approved, ATII will ask the holders of ATII Ordinary Shares to approve and adopt, by Special Resolution of the holders of ATII Ordinary Shares, the Organizational Documents Proposal in connection with the replacement of the Current Charter, under the Companies Act, with the Proposed Organizational Documents, under the DGCL. The ATII Board has unanimously approved the Organizational Documents Proposal and recommended its approval to the holders of ATII Ordinary Shares at the extraordinary general meeting, and believes the Organizational Documents Proposal is necessary to adequately address the needs of Pubco following the Closing.

For additional information, please see the section titled “Proposal No. 5 – The Organizational Documents Proposal”.

Proposal No. 6 — The Advisory Organizational Documents Proposals (page 144)

ATII will ask the holders of ATII Ordinary Shares to approve, by Ordinary Resolution of the holders of ATII Ordinary Shares, on a non-binding advisory basis, six (6) separate Advisory Organizational Documents Proposals in connection with the replacement of the Current Charter, under the Companies Act, with the Proposed Organizational Documents, under the Companies Act, DGCL and DLLCA. The ATII Board has unanimously approved each of the Advisory Organizational Documents Proposals and recommended their approval to the holders of ATII Ordinary Shares, and believes each of the Advisory Organizational Documents Proposals are necessary to adequately address the needs of Pubco following the Closing.

A brief summary of each of the Advisory Organizational Documents Proposals is set forth below. These summaries are qualified in their entirety by reference to the complete text of the Proposed Organizational Documents, copies of which are attached to this proxy statement/prospectus as Annex B-1 and Annex B-2.

(A)Advisory Organizational Documents Proposal 6A (Authorized Shares) — to approve and adopt an amendment to the Current Charter, with effect from the Domestication Merger Effective Time, to authorize the amendment and redesignation of the authorized share capital of ATII from (a) 400,000,000 ATII Ordinary Shares and 1,000,000 preference shares, par value $0.0001 per share, of ATII to (b) [500,000,000] shares of Pubco Common Stock and [5,000,000] shares of preferred stock of Pubco, par value $0.0001 per share.

(B)Advisory Organizational Documents Proposal 6B (Exclusive Forum Provision) — to approve and adopt an amendment to the Current Charter, with effect from the Domestication Merger Effective Time, to authorize adopting Delaware as the exclusive forum for certain stockholder litigation and adopting the federal district courts of the United States as the exclusive forum for resolving complaints asserting a cause of action under the Securities Act of 1933, as amended, with effect from the Domestication Merger Effective Time.

(C)Advisory Organizational Documents Proposal 6C (Required Vote to Amend Charter) — to approve and adopt an amendment to the Current Charter, with effect from the Domestication Merger Effective Time, to authorize provisions providing that the affirmative vote of at least two-thirds of the voting power of all the then outstanding shares of capital stock of Pubco entitled to vote thereon, voting together as a single class, will be required to amend, alter, repeal or rescind any provision of Articles            of the Proposed Charter in accordance with the DGCL and the Companies Act.

(D)Advisory Organizational Documents Proposal 6D (Removal of Directors) — to approve and adopt an amendment to the Current Charter, with effect from the Domestication Merger Effective Time, to authorize provisions permitting the removal of a director, with or without cause, by the affirmative vote of at least two-thirds of the outstanding shares of capital stock of Pubco entitled to vote generally in the election of directors, voting together as a single class.

(E)Advisory Organizational Documents Proposal 6E (Stockholder Action by Written Consent) — to approve and adopt an amendment to the Current Charter, with effect from the Domestication Merger Effective Time, to authorize provisions that require or permit stockholders to take action at an annual or special meeting and prohibit stockholder action by written consent in lieu of a meeting.

(F)Advisory Organizational Documents Proposal 6F (Additional Changes) — to approve and adopt an amendment to the Current Charter, with effect at the Domestication Merger Effective Time, to authorize certain additional changes, including, among other things, (i) making Pubco’s corporate existence perpetual and (ii) removing certain provisions related to ATII’s status as a blank check company that will no longer be applicable upon Closing, all of which the ATII Board believes is necessary to adequately address the needs of Pubco after the Business Combination.

For additional information, see the section titled “Proposal No. 6 – The Advisory Organizational Documents Proposals.”

Proposal No. 7 — The Equity Incentive Plan Proposal (page 152)

ATII will ask the holders of ATII Ordinary Shares to approve and adopt, by Ordinary Resolution of the holders of ATII Ordinary Shares, the Forge Nano Holdings Inc. 2026 Omnibus Incentive Compensation Plan (the “2026 Equity Plan”), a copy of which is attached to this proxy statement/prospectus as Annex G (the “Equity Incentive Plan Proposal”). The ATII Board has unanimously approved the Equity Incentive Plan Proposal and recommended its approval to the holders of ATII Ordinary Shares at the extraordinary general meeting

For additional information, see “Proposal No. 7 – the Equity Incentive Plan Proposal.”

Proposal No. 8 — The Adjournment Proposal (page 157)

If, based on the tabulated vote, there are not sufficient votes at the time of the extraordinary general meeting to authorize ATII to consummate the Business Combination (because any of the Condition Precedent Proposals has not been approved (including as a result of the failure of any other cross-conditioned Condition Precedent Proposals to be approved)), the ATII Board may submit a proposal to the holders of ATII Ordinary Shares to approve, by way of an Ordinary Resolution of the holders of ATII Ordinary Shares, the adjournment of the extraordinary general meeting to a later date or dates, if necessary, to permit further solicitation and vote of proxies.

For additional information, see “Proposal No. 8 – The Adjournment Proposal.”

Condition Precedent Proposals

Each of Proposal Nos. 1, 2, 3, 4, 5 and 7 are cross-conditioned on the approval of each other. The Advisory Organizational Documents Proposals 6A-F and the Adjournment Proposal are not cross-conditioned upon the approval of any other proposal set forth in this proxy statement/prospectus. Notwithstanding the order of the resolutions on the notice to the extraordinary general meeting, the Adjournment Proposal may be presented first to the holders of ATII Ordinary Shares if, based on the tabulated vote collected at the time of the extraordinary general meeting, there are insufficient votes for, or otherwise in connection with, the approval of the Condition Precedent Proposals. The transactions contemplated by the Merger Agreement will be consummated only if the Condition Precedent Proposals are approved at the extraordinary general meeting.

Date, Time and Place of the Extraordinary General Meeting

The extraordinary general meeting will be held at            Eastern Time on           , 2026 and will be a virtual meeting conducted via live webcast at            (the “extraordinary general meeting website”). For the purposes of Cayman Islands law and the Current Charter, the physical location of the extraordinary general meeting will be at the offices of ATII at.

Registering for the Extraordinary General Meeting

Any holder of ATII Ordinary Shares wishing to attend the extraordinary general meeting virtually must pre-register for the extraordinary general meeting at            by            Eastern Time on           , 2026. For purposes of attendance at the extraordinary general meeting, all references in this proxy statement to “present” shall mean virtually present at the extraordinary general meeting. To register for the extraordinary general meeting, please follow these instructions as applicable to the nature of your ownership of ATII Ordinary Shares:

Voting Power; Record Date

Only holders of ATII Ordinary Shares at the close of business on the Record Date are entitled to notice of the extraordinary general meeting and to vote at the extraordinary general meeting pursuant to the Companies Act and the Current Charter. A list of holders of ATII Ordinary Shares entitled to vote at the extraordinary general meeting will be available at our principal executive offices located at 2093 Philadelphia Pike #1968, Claymont, DE 19703, during regular business hours for a period of no less than ten days prior to the extraordinary general meeting, as well as electronically at the extraordinary general meeting website. As of            , 2026, which is the Record Date for the extraordinary general meeting, there were 29,590,000 ATII Ordinary Shares outstanding, of which 23,000,000 were ATII Public Shares held by persons other than the Insiders. Holders of ATII Ordinary Shares will be entitled to one vote for each ATII Ordinary Share owned at the close of business on the Record Date.

If you hold your ATII Ordinary Share in “street name”, you should instruct your bank, broker or other nominee how to vote your ATII Ordinary Shares at the extraordinary general meeting in accordance with the voting instruction form that you will receive from your bank, broker or other nominee. Your bank, broker or other nominee cannot vote on any of the proposals, including the Business Combination Proposal, without your instructions. ATII Warrants do not have voting rights.

The presence, in person or represented by proxy, of the holders of a majority of the ATII Ordinary Shares entitled to vote on the Record Date will constitute a quorum at the extraordinary general meeting pursuant to the Companies Act and the Current Charter. As of the Record Date, the presence, in person or represented by proxy, of the holders of at least 14,795,001 ATII Ordinary Shares would be required to achieve a quorum at the extraordinary general meeting. Because the Sponsor and BTIG have the right to vote, collectively, 6,590,000 ATII Ordinary Shares and will attend the extraordinary general meeting in connection with the Proposed Transaction, the presence at the extraordinary general meeting of additional holders of 8,205,001 ATII Ordinary Shares would be required to achieve a quorum at the extraordinary general meeting. Abstentions and broker non-votes, while considered present for the purposes of establishing a quorum at the extraordinary general meeting, will not count as a vote cast at the extraordinary general meeting and otherwise will have no effect on a particular proposal under the Companies Act and the Current Charter. In the event that quorum is not present at the extraordinary general meeting, it is expected that the extraordinary general meeting will be adjourned to solicit additional proxies.

Abstentions and Broker Non-Votes

If your ATII Ordinary Shares are held in a stock brokerage account or by a bank or other nominee, you are considered the “beneficial holder” of the ATII Ordinary Shares held for you in what is known as “street name.” If this is the case, this proxy statement/prospectus may have been forwarded to you by your brokerage firm, bank or other nominee, or its agent, and you may need to obtain a proxy form from the institution that holds your ATII Ordinary Shares and follow the instructions included on that form regarding how to instruct your broker, bank or nominee as to how to vote your ATII Ordinary Shares. Under the rules of various national and regional securities exchanges, your broker, bank, or nominee cannot vote your ATII Ordinary Shares with respect to non-discretionary matters unless you provide instructions on how to vote in accordance with the information and procedures provided to you by your broker, bank, or nominee. We believe all the proposals presented to the holders of ATII Ordinary Shares will be considered non-discretionary and therefore your broker, bank, or nominee cannot vote your ATII Ordinary Shares without your instruction. Your bank, broker, or other nominee can vote your ATII Ordinary Shares only if you provide instructions on how to vote. As the beneficial holder of the ATII Ordinary Shares, you have the right to direct your broker, bank or other nominee as to how to vote your ATII Ordinary Shares and you should instruct your broker to vote your ATII Ordinary Shares in accordance with directions you provide. If you do not provide voting instructions to your broker on a particular proposal on which your broker does not have discretionary authority to vote, your ATII Ordinary Shares will not be voted on that proposal. This is called a “broker non-vote.”

Abstentions and broker non-votes, while considered present for the purposes of establishing a quorum at the extraordinary general meeting, will not count as votes cast at the extraordinary general meeting, and otherwise will have no effect on a particular proposal under the Companies Act and the Current Charter.

Vote Required for Approval

The approval and adoption of the Business Combination Proposal, the Director Election Proposal, the Stock Issuance Proposal, the Advisory Organizational Documents Proposal and the Equity Incentive Plan Proposal requires an Ordinary Resolution of the holders of ATII Ordinary Shares under the Companies Act and the Current Charter, being a resolution passed by the affirmative vote of a simple majority of the votes cast by holders of the ATII Ordinary Shares as, being entitled to do so, vote in person or, where proxies are allowed, by proxy at the extraordinary general meeting (assuming presence of a quorum).

The approval and adoption of the Domestication Merger Proposal and the Organizational Documents Proposal requires a Special Resolution of the holders of ATII Ordinary Shares under Companies Act and the Current Charter, being a resolution passed by the affirmative vote of at least two-thirds of votes cast by holders of the ATII Ordinary Shares as, being entitled to do so, vote in person or, where proxies are allowed, by proxy at the extraordinary general meeting (assuming presence of quorum).

Each Condition Precedent Proposal is conditioned upon the approval of the other Condition Precedent Proposals. Therefore, if all Condition Precedent Proposals are not approved, none of the Condition Precedent Proposals will have any effect, even if certain Condition Precedent Proposals are approved by holders of ATII Ordinary Shares. The Advisory Organizational Documents Proposals are not conditioned upon any other proposal.

The approval of the Adjournment Proposal requires an Ordinary Resolution of the holders of ATII Ordinary Shares under the Companies Act and the Current Charter, being a resolution passed by the affirmative vote of a simple majority of the votes cast by the holders of the ATII Ordinary Shares as, being entitled to do so, vote in person or, where proxies are allowed, by proxy at the extraordinary general meeting (assuming presence of a quorum). The Adjournment Proposal is not conditioned upon any other proposal.

The Sponsor, which includes among its members each of the ATII Directors and the officers of ATII, and BTIG have the right to vote, collectively, 6,590,000 ATII Ordinary Shares. As a result, 8,205,001 additional votes of holders of ATII Ordinary Shares will be required to approve and adopt, by Ordinary Resolution of the holders of ATII Ordinary Shares, the Business Combination Proposal, the Director Election Proposal, the Stock Issuance Proposal, the Advisory Organizational Documents Proposals, the Equity Incentive Plan Proposal and, if presented, the Adjournment Proposal, while 13,136,667 additional votes of holders of ATII Ordinary Shares will be required to approve and adopt, by Special Resolution of the holders of ATII Ordinary Shares, the Domestication Merger Proposal and the Organizational Documents Proposal.

Stock Ownership and Interests of Certain Persons

ATII Ordinary Shares Held by Insiders

The Insiders, including the Sponsor, which includes among its members each of the ATII Directors and officers of ATII, and BTIG have each agreed to vote all of their respective Founder Shares and ATII Private Shares purchased in a private placement concurrently with the IPO in favor of the proposals being presented at the extraordinary general meeting. As of the Record Date, the Sponsor and BTIG beneficially owned and were entitled to vote, collectively, 6,590,000 ATII Ordinary Shares. As a result, as of the Record Date, the Insiders and BTIG owned, collectively, approximately 22.27% of the issued and outstanding ATII Ordinary Shares. Accordingly, 8,205,001 additional votes of holders of ATII Ordinary Shares will be required to approve and adopt, by Ordinary Resolution of the holders of ATII Ordinary Shares, each of the Business Combination Proposal, the Director Election Proposal, the Stock Issuance Proposal, the Advisory Organizational Documents Proposals, the Equity Incentive Plan Proposal and, if presented, the Adjournment Proposal, while 13,136,667 additional votes of holders of ATII Ordinary Shares will be required to approve and adopt, by Special Resolution of the holders of ATII Ordinary Shares, each of the Domestication Merger Proposal and the Organizational Documents Proposal.

We currently expect that each of the Insiders and BTIG will vote all of their respective ATII Ordinary Shares (1) “FOR” the Business Combination Proposal, (2) “FOR” the Domestication Merger Proposal, (3) “FOR” the Director Election Proposal, (4) “FOR” the Stock Issuance Proposal, (5) “FOR” the Organizational Documents Proposal, (6) “FOR” the Advisory Organizational Documents Proposal, (7) “FOR” the Equity Incentive Plan Proposal and (8) “FOR” the Adjournment Proposal, if needed.

Voting at the Extraordinary General Meeting

You can vote at the extraordinary general meeting, which will be held at           Eastern Time on           , 2026, at            (unless the extraordinary general meeting is adjourned or postponed).

You may also authorize the persons named as proxies on the proxy card to vote your ATII Ordinary Shares by returning the proxy card in advance by mail, over the Internet or by telephone. Although ATII offers three different voting methods, ATII encourages you to vote over the Internet or by phone as ATII believes they are the most cost-effective methods. We also recommend that you vote as soon as possible, even if you are planning to attend the extraordinary general meeting, so that the vote count will not be delayed. Both the Internet and the telephone provide convenient, cost-effective and reliable alternatives to returning your proxy card by mail. If you choose to vote your shares over the Internet or by telephone, there is no need for you to submit your proxy card by mail.

To Vote Over the Internet:

Vote at           in advance of the extraordinary general meeting. The Internet voting system is available 24 hours until 11:59 p.m. Eastern Time on           , 2026. Once you enter the Internet voting system, you can record and confirm (or change) your voting instructions.

To Vote by Telephone:

Use the telephone number shown on your proxy card. The telephone voting system is available 24 hours per day in the United States until 11:59 p.m. Eastern Time on           , 2026. Once you enter the telephone voting system, a series of prompts will tell you how to record and confirm (or change) your voting instructions.

To Vote by Proxy Card:

If you received a proxy card, mark your voting instructions on the card and sign, date and return it in the postage-paid envelope provided. For your mailed proxy card to be counted, we must receive it before            Eastern Time on           , 2026.

All ATII Ordinary Shares represented by properly signed and dated proxies received by the deadline indicated above will be voted at the extraordinary general meeting in accordance with the instructions of the holder of such ATII Ordinary Shares. Properly signed and dated proxies that do not contain voting instructions will be voted: (1) “FOR” the Business Combination Proposal; (2) “FOR” the Domestication Merger Proposal; (3) “FOR” the Director Election Proposal; (4) “FOR” the Stock Issuance Proposal; (5) “FOR” the Organizational Documents Proposal; (6) “FOR” the Advisory Organizational Documents Proposal; (7) “FOR” the Equity Incentive Plan Proposal; and (8) “FOR” the Adjournment Proposal, if needed. Proxy cards that are returned without a signature will not be counted as present at the extraordinary general meeting and cannot be voted under the Companies Act and the Current Charter.

If your ATII Ordinary Shares are held in “street name” through a bank, broker or other nominee, you may vote through your bank, broker or other nominee by completing and returning the voting form provided by your bank, broker or other nominee or attending the extraordinary general meeting and voting using your control number, or, if you did not obtain a control number, contacting your bank, broker or other nominee to obtain a control number so that you may vote. If such a service is provided, you may vote over the Internet or telephone through your bank, broker or other nominee by following the instructions on the voting form provided by your bank, broker or other nominee. If you do not return your bank’s, broker’s or other nominee’s voting form, via the Internet or telephone through your bank, broker or other nominee, if possible, or do not attend and vote at the extraordinary general meeting, your shares will not be considered present for the purposes of establishing a quorum at the extraordinary general meeting, will not count as votes cast at the extraordinary general meeting, and otherwise will have no effect on a particular proposal under the Companies Act and the Current Charter.

Revocability of Proxies

Any proxy given by a holder of ATII Ordinary Shares may be revoked at any time prior to the extraordinary general meeting by doing any of the following:

If you hold your ATII Ordinary Shares in “street name,” you should contact your bank, broker or other nominee for instructions regarding how to change your vote.

Any adjournment, postponement or other delay of the extraordinary general meeting, including pursuant to the Adjournment Proposal for the purpose of soliciting additional proxies, will allow holders of ATII Ordinary Shares who have already sent in their proxies for the extraordinary general meeting to revoke them at any time prior to their use at the adjourned, postponed or delayed extraordinary general meeting.

ATII Board’s Recommendation (page 104)

The ATII Board, after considering the factors more fully described in the enclosed proxy statement/prospectus, has unanimously: (i) determined that the Merger Agreement and the transactions contemplated thereby, including the Business Combination, are fair to and in the best interests of ATII and the holders of ATII Ordinary Shares, (ii) approved and declared advisable the Merger Agreement and the transactions contemplated therein, including the Business Combination, (iii) directed that the adoption of the Merger Agreement be submitted to a vote of the holders of ATII Ordinary Shares at the extraordinary general meeting and (iv) resolved to recommend the adoption of the Merger Agreement and the approval of the Business Combination by holders of ATII Ordinary Shares at the extraordinary general meeting. The ATII Board unanimously recommends that you vote: (1) “FOR” the Business Combination Proposal; (2) “FOR” the Domestication Merger Proposal; (3) “FOR” the Director Election Proposal; (4) “FOR” the Stock Issuance Proposal; (5) “FOR” the Organizational Documents Proposal; (6) “FOR” the Advisory Organizational Documents Proposal; (7) “FOR” the Equity Incentive Plan Proposal; and (8) “FOR” the Adjournment Proposal.

For a more complete description of the ATII Board’s reasons for the approval of the Business Combination and the recommendation of the ATII Board, see the section titled “Proposal No. 1 – The Business Combination Proposal – the ATII Board Reasons for the Approval of the Business Combination.”

When you consider the recommendation of the ATII Board to vote in favor of approval and adoption of the proposals, you should keep in mind that the Sponsor, the ATII Directors and the officers of ATII have interests in the Business Combination that are different from or in addition to (and which may conflict with) your interests as a holder of ATII Ordinary Shares.

The existence of financial and personal interests of one or more ATII Directors may result in a conflict of interest on the part of such ATII Director(s) between what he, she or they may believe is in the best interests of ATII and the holders of ATII Ordinary Shares and what he, she or they may believe is best for himself, herself or themselves in determining to recommend that holders of ATII Ordinary Shares vote to approve and adopt the proposals. In addition, ATII’s officers have interests in the Business Combination that may conflict with your interests as a holder of ATII Ordinary Shares. See “Proposal No. 1 – The Business Combination Proposal — Certain Interests of ATII’s Directors and Officers and Others in the Business Combination.”

Redemption Rights

Pursuant to the Current Charter, an ATII Public Shareholder may elect to have ATII redeem all or a portion of the ATII Public Shares held by such ATII Public Shareholder in exchange for cash if the Business Combination (or any other initial business combination) is consummated during the Completion Window. If the Business Combination is approved and completed during the Completion Window, an ATII Public Shareholder will be entitled to receive cash in exchange for any ATII Public Shares held by such ATII Public Shareholder only if:

ATII Public Shareholders must complete the procedures for electing to redeem their ATII Public Shares in the manner described above prior to       Eastern Time on        , 2026 (up to two business days prior to the initially scheduled vote on the Business

Combination Proposal and the other proposals included in this proxy statement/prospectus) in order for their ATII Public Shares to be redeemed. Holders of ATII Public Units must elect to separate any ATII Public Units held by them into the underlying ATII Public Shares and ATII Public Warrants prior to exercising their redemption rights with respect to the ATII Public Shares. ATII Public Shareholders may elect to redeem their ATII Public Shares even if they vote “FOR” the Business Combination Proposal. If the Business Combination (or any other initial business combination) is not consummated during the Completion Window, the ATII Public Shares will be returned to their respective holder, broker or bank.

If the Business Combination (or any other initial business combination) is consummated during the Completion Window, and if any ATII Public Shareholder properly exercises their right to redeem all or a portion of the ATII Public Shares that they hold and timely tenders or delivers its ATII Public Share certificates (if any) and other redemption forms (as applicable) to the Transfer Agent, ATII will redeem such ATII Public Shares for a per-share price, payable in cash, equal to quotient obtained by dividing (1) the aggregate amount then on deposit in the Trust Account calculated as of two business days prior to the consummation of the Business Combination (or any other initial business combination) during the Completion Window, including interest earned on the Trust Account (net of taxes paid or payables, if any), by (2) the aggregate number of ATII Public Shares then issued and outstanding. For illustrative purposes, as of December 31, 2025, this would have amounted to approximately $10.43 per issued and outstanding ATII Public Share. If any ATII Public Shareholder exercises their redemption rights in full, then they will be electing to exchange all of their ATII Public Shares in exchange for cash and will thereafter no longer own ATII Public Shares. See “Extraordinary General Meeting of ATII — Redemption Rights” for a detailed description of the procedures to be followed if you wish to redeem your ATII Public Shares in exchange for cash.

Notwithstanding the foregoing, pursuant to the Current Charter, any ATII Public Shareholder, together with any affiliate of such ATII Public Shareholder or any other person with whom such ATII Public Shareholder is acting in concert or as a “group” (as defined in Section 13(d)(3) of the Exchange Act), will be restricted from redeeming its ATII Public Shares with respect to more than an aggregate of 15% of the ATII Public Shares then issued and outstanding without ATII’s prior consent. Accordingly, if any ATII Public Shareholder, alone or acting in concert or as a “group,” seeks to redeem more than an aggregate of 15% of the ATII Public Shares then issued and outstanding, then any such ATII Public Shares in excess of that 15% limit would not be redeemed without ATII’s prior consent.

Holders of the ATII Warrants will not have Redemption Rights with respect to the ATII Warrants pursuant to the terms of the ATII Warrant Agreement and the Current Charter.

Ownership of Pubco after the Closing

Upon consummation of the Business Combination, the post-Closing share ownership of Pubco under (1) the No Additional Redemptions Scenario, (2) the 25% Redemptions Scenario, (3) the 50% Redemptions Scenario, (4) the 75% Redemptions Scenario and (5) the Maximum Redemptions Scenario, excluding the dilutive effect of Pubco SPAC Warrants, Pubco Forge Nano Warrants, Pubco Ascent Warrants, Pubco Options, PIPE Warrants, Reset PIPE Warrants and Earn-Out Shares, would be as follows:

The following table illustrates varying ownership levels of Pubco immediately following the Business Combination on a fully diluted basis⁽¹⁾:

In addition to the changes in percentage ownership depicted above, variation in the levels of redemptions will impact the dilutive effect of certain equity issuances related to the Business Combination, which would not otherwise be present in an underwritten public offering. Increasing levels of redemptions will increase the dilutive effect of these issuances on non-redeeming holders of the ATII Public Shares.

For more information, please see the sections entitled “Unaudited Pro Forma Condensed Combined Financial Information” and “Proposal No. 1 — The Business Combination Proposal — Ownership of Pubco After the Closing.”

All of the relative percentages above are for illustrative purposes only and are based upon certain assumptions as described in the section entitled “Unaudited Pro Forma Condensed Combined Financial Information.” For more information, including the ownership percentages in the No Additional Redemptions Scenario and the effect of certain dilutive securities, see the section entitled “Proposal No. 1 – The Business Combination Proposal — Ownership of Pubco After the Closing.”

Proxy Solicitation

The ATII Board is soliciting your proxy and ATII will bear the cost of soliciting proxies.         has been retained to assist with the solicitation of proxies. ATII expects to pay         a fee of $         , plus certain costs associated with additional services, as necessary, and         will be reimbursed for its reasonable out-of-pocket expenses for these and other advisory services in connection with the extraordinary general meeting. Forms of proxies and proxy materials may also be distributed through brokers, custodians and other like parties to the beneficial owners of ATII Ordinary Shares, in which case these parties will be reimbursed for their reasonable out-of-pocket expenses in accordance with SEC and Nasdaq regulations. Proxies may also be solicited in person or by telephone, facsimile, electronic mail or other electronic medium by         or, without additional compensation, by ATII, the ATII Directors or any officers and employees of ATII. This solicitation is being made by mail but also may be made by telephone. ATII, the ATII Directors and any officers and employees of ATII may also solicit proxies online. ATII will file with the SEC all scripts and other electronic communications as proxy soliciting materials.

If a holder of ATII Ordinary Shares grants a proxy, such holder may still vote its ATII Ordinary Shares in person if it revokes its proxy before the extraordinary general meeting. A holder of ATII Ordinary Shares also may change its vote by submitting a later-dated proxy as described in “Extraordinary General Meeting of ATII — Revoking Your Proxy.”

Anticipated Date of Consummation of the Business Combination

Assuming the timely satisfaction of necessary closing conditions, including the approval by the holders of ATII Ordinary Shares, by Ordinary Resolution of the holders of ATII Ordinary Shares, of the Business Combination Proposal, we currently anticipate that the Business Combination will be consummated in the third calendar quarter of 2026. However, the exact timing of consummation of the Business Combination cannot be predicted because the Business Combination is subject to closing conditions specified in the Merger Agreement and summarized in this proxy statement/prospectus, many of which are outside of our control.

Regulatory Matters

Neither ATII nor Forge Nano is aware of any material regulatory approvals or actions that are required for completion of the Business Combination, other than the regulatory notices and approvals discussed in “Proposal No. 1 – The Business Combination Proposal — Merger Agreement — Closing Conditions — Conditions to the Obligations of Each Party.” It is presently contemplated that if any such additional regulatory approvals or actions are required, those approvals or actions will be sought. There can be no assurance, however, that any additional approvals or actions will be obtained.

Implications of Being an Emerging Growth Company

ATII is, and Pubco expects to be, an “emerging growth company” as defined in the Jumpstart Our Business Startups (the “JOBS Act”). As an “emerging growth company,” ATII takes, and Pubco may (and intends to) take, advantage of specified reduced reporting and other requirements that are otherwise applicable to public companies. These provisions include, among other things:

ATII and/or Pubco may choose to take advantage of some, but not all, of these reduced burdens. For example, ATII and/or Pubco have (i) taken advantage of the reduced reporting requirement with respect to disclosure regarding executive compensation arrangements and (ii) presented only two (2) years of audited financial statements in this proxy statement/prospectus. In addition, ATII and/or Pubco may take advantage of the exemption from the auditor attestation requirement in the assessment on the effectiveness of their internal control over financial reporting. In addition, while ATII and/or Pubco have elected to avail themselves of the exemption to adopt new or revised accounting standards until those standards apply to private companies, ATII and/or Pubco are permitted and may elect to early adopt certain new or revised accounting standards for which the respective standard allows for early adoption. We have elected to use this extended transition period for complying with certain new or revised accounting standards that have different effective dates for public and private companies until the earlier of the date that ATII and/or Pubco (i) are no longer an “emerging growth company” as defined in the JOBS Act or (ii) affirmatively and irrevocably opt out of the extended transition period provided in the JOBS Act. For as long as ATII and/or Pubco take advantage of these reduced reporting obligations, the information that ATII and/or Pubco provide to holders of ATII Ordinary Shares or shares of Pubco Common Stock, as applicable, may be different from information provided by other similarly situated public companies.

ATII and/or Pubco will remain an “emerging growth company” until the earlier of (1) the last day of the fiscal year (a) following February 12, 2030, (b) in which it has total annual gross revenue of at least $1.235 billion, or (c) in which it is deemed to be a large accelerated filer, which means the market value of its common equity that is held by non-affiliates exceeds $700 million as of the end of the prior fiscal year’s second fiscal quarter and (2) the date on which it has issued more than $1.00 billion in non-convertible debt securities during the prior three-year period.

Implications of Being a Smaller Reporting Company

Additionally, ATII is, and Pubco expects to be, a “smaller reporting company,” meaning that the market value of its ATII Ordinary Shares or shares of Pubco Common Stock, as applicable, held by non-affiliates is less than $700 million and annual revenue is less than $100 million during the most recently completed fiscal year. As such, ATII and/or Pubco are eligible for exemptions from various reporting requirements applicable to other public companies that are not “smaller reporting companies,” including, but not limited to, reduced disclosure obligations regarding executive compensation.

ATII and/or Pubco will remain a “smaller reporting company” until the last day of the fiscal year in which (1) the market value of ATII Ordinary Shares or shares of Pubco Common Stock, as applicable, held by non-affiliates exceeds $250 million as of the prior June 30 or (2) annual revenues exceed $100 million during such completed fiscal year and the market value of ATII Ordinary Shares or shares of Pubco Common Stock, as applicable, held by non-affiliates exceeds $700 million as of the prior June 30.

Stock Exchange Listing of Pubco Common Stock and Pubco Warrants

Pubco intends to apply to list the (i) Pubco Common Stock and (ii) Pubco SPAC Warrants that were originally issued as part of the ATII Public Units on Nasdaq under the proposed symbols NANO and NANOW, respectively, upon the Closing.

Pursuant to the terms of the Merger Agreement, as a closing condition, Pubco is required to cause the Pubco Common Stock to be issued in connection with the Business Combination to be approved for listing on Nasdaq, but there can be no assurance that such listing condition will be met. If such listing condition is not met, the Business Combination will not be consummated unless the listing condition is waived by all of the parties to the Merger Agreement. It is important for you to know that, at the time of the extraordinary general meeting, Pubco may not have received from Nasdaq either confirmation of the listing of the Pubco Common Stock or that approval will be obtained prior to the consummation of the Business Combination. As a result, you may be asked to vote to approve the Business Combination and the other proposals included in this proxy statement/prospectus without such confirmation, and, further, it is possible that such confirmation may never be received and the Business Combination could still be consummated if such condition is waived by all of the parties to the Merger Agreement and therefore the Pubco Common Stock would not be listed on any nationally recognized securities exchange upon the Closing.

The ATII Public Units, ATII Public Shares and ATII Public Warrants are each currently quoted on Nasdaq. At the Domestication Merger Effective Time, the separate corporate existence of ATII will cease and the ATII Public Units, ATII Public Shares and ATII

Public Warrants will each no longer be publicly traded and will be delisted from Nasdaq. In addition, the ATII Public Units, ATII Public Shares and ATII Public Warrants will each be deregistered under the Exchange Act, and ATII will no longer file periodic reports with the SEC.

U.S. Federal Income Tax Considerations

For a discussion summarizing certain material U.S. federal income tax considerations of the Domestication Merger and an exercise of Redemption Rights in connection with the Business Combination, please see “Material U.S. Federal Income Tax Considerations”.

Summary Unaudited Pro Forma Condensed Combined Financial Information

The following summary unaudited pro forma condensed combined financial information (the “Summary Pro Forma Information”) gives effect to the transactions contemplated by the Business Combination and related transactions. The Business Combination will be accounted for as a reverse recapitalization in accordance with GAAP. Under this method of accounting, although ATII will acquire all of the outstanding equity interests of Forge Nano in the Business Combination, ATII will be treated as the “acquired” company for financial reporting purposes. Accordingly, the Business Combination will be reflected as the equivalent of Forge Nano issuing shares for the net assets of ATII, followed by a recapitalization whereby no goodwill or other intangible assets are recorded. Operations prior to the Business Combination will be those of Forge Nano.

The summary unaudited pro forma condensed combined balance sheet data as of December 31, 2025, gives effect to the Business Combination and related transactions as if they had occurred on December 31, 2025. The summary unaudited pro forma condensed combined statement of operations data for the year ended December 31, 2025, give effect to the Business Combination and related transactions as if they had occurred on January 1, 2025, the beginning of the earliest period presented.

The Summary Pro Forma Information has been derived from, should be read in conjunction with, the more detailed unaudited pro forma condensed combined financial information included in the section entitled “Unaudited Pro Forma Condensed Combined Financial Information” in this proxy statement/prospectus and the accompanying notes thereto. The unaudited pro forma condensed combined financial information is based upon, and should be read in conjunction with, the historical financial statements and related notes of ATII and Forge Nano for the applicable period included in this proxy statement/prospectus. The Summary Pro Forma Information has been presented for informational purposes only and is not necessarily indicative of what Pubco’s financial position or results of operations actually would have been had the Business Combination and related transactions been completed as of the dates indicated. In addition, the Summary Pro Forma Information does not purport to project the future financial position or operating results of Pubco following the reverse recapitalization.

The unaudited pro forma condensed combined financial information has been prepared using the assumptions below with respect to the potential redemption for cash of ATII Public Shares:

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Summary Risk Factors

ATII believes it is important to communicate its expectations to the holders of ATII Ordinary Shares. However, there may be events in the future that neither ATII nor Forge Nano are able to predict accurately or over which they have control. The section in this proxy statement/prospectus entitled “Risk Factors” and the other cautionary language discussed in this proxy statement/prospectus provide examples of certain risks, uncertainties and events that may cause actual results to differ materially from the expectations described by ATII or Forge Nano in such forward-looking statements. Set forth below is only a summary of certain principal risks associated with an investment in our securities. You should carefully consider the following discussion of risks, as well as the discussion of risks included elsewhere in this proxy statement/prospectus, including those described under “Risk Factors.”

The ATII Board, after considering the factors more fully described in the enclosed proxy statement/prospectus, has unanimously: (i) determined that the Merger Agreement and the transactions contemplated thereby, including the Business Combination, are fair to and in the best interests of ATII and the holders of ATII Ordinary Shares, (ii) approved and declared advisable the Merger Agreement and the transactions contemplated thereby, including the execution, delivery and performance of the Merger Agreement, (iii) directed that the adoption of the Merger Agreement be submitted to a vote of the holders of ATII Ordinary Shares at the extraordinary general meeting and (iv) resolved to recommend the adoption of the Merger Agreement and the approval of the Business Combination Proposal by the holders of ATII Ordinary Shares at the extraordinary general meeting.

Pursuant to the Current Charter, an ATII Public Shareholder may elect to have ATII redeem all or a portion of the ATII Public Shares held by such ATII Public Shareholder in exchange for cash if the Business Combination (or any other initial business combination) is consummated during the Completion Window. If the Business Combination is approved and completed during the Completion Window, an ATII Public Shareholder will be entitled to receive cash in exchange for any ATII Public Shares held by such ATII Public Shareholder only if:

ATII Public Shareholders must complete the procedures for electing to redeem their ATII Public Shares in the manner described above prior to       Eastern Time on        , 2026 (up to two business days prior to the initially scheduled vote on the Business

Combination Proposal and the other proposals included in this proxy statement/prospectus) in order for their ATII Public Shares to be redeemed. Holders of ATII Public Units must elect to separate any ATII Public Units held by them into the underlying ATII Public Shares and ATII Public Warrants prior to exercising their redemption rights with respect to the ATII Public Shares. ATII Public Shareholders may elect to redeem their ATII Public Shares even if they vote “FOR” the Business Combination Proposal. If the Business Combination (or any other initial business combination) is not consummated during the Completion Window, the ATII Public Shares will be returned to their respective holder, broker or bank.

If the Business Combination (or any other initial business combination) is consummated during the Completion Window, and if any ATII Public Shareholder properly exercises their right to redeem all or a portion of the ATII Public Shares that they hold and timely tenders or delivers its ATII Public Share certificates (if any) and other redemption forms (as applicable) to the Transfer Agent, ATII will redeem such ATII Public Shares for a per-share price, payable in cash, equal to quotient obtained by dividing (1) the aggregate amount then on deposit in the Trust Account calculated as of two business days prior to the consummation of the Business Combination (or any other initial business combination) during the Completion Window, including interest earned on the Trust Account (net of taxes paid or payables, if any), by (2) the aggregate number of ATII Public Shares then issued and outstanding. For illustrative purposes, as of December 31, 2025, this would have amounted to approximately $10.43 per issued and outstanding ATII Public Share. If any ATII Public Shareholder exercises their redemption rights in full, then they will be electing to exchange all of their ATII Public Shares in exchange for cash and will thereafter no longer own ATII Public Shares. See “Extraordinary General Meeting of ATII — Redemption Rights” for a detailed description of the procedures to be followed if you wish to redeem your ATII Public Shares in exchange for cash.

Notwithstanding the foregoing, pursuant to the Current Charter, any ATII Public Shareholder, together with any affiliate of such ATII Public Shareholder or any other person with whom such ATII Public Shareholder is acting in concert or as a “group” (as defined in Section 13(d)(3) of the Exchange Act), will be restricted from redeeming its ATII Public Shares with respect to more than an aggregate of 15% of the ATII Public Shares then issued and outstanding without ATII’s prior consent. Accordingly, if any ATII Public Shareholder, alone or acting in concert or as a “group,” seeks to redeem more than an aggregate of 15% of the ATII Public Shares then issued and outstanding, then any such ATII Public Shares in excess of that 15% limit would not be redeemed without ATII’s prior consent.

Holders of the ATII Warrants will not have Redemption Rights with respect to the ATII Warrants pursuant to the terms of the ATII Warrant Agreement and the Current Charter.

The following table illustrates the changes in net tangible book value and dilution to existing shareholders at varying redemption levels (in thousands, except share and per share data).

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The following table illustrates the as-adjusted net tangible book value to ATII Shareholders and decrease in net tangible book value to ATII Shareholders as a result of transaction costs incurred by ATII, the PIPE Financing, and funds released from the Trust Account upon consummation of the Business Combination (in thousands, except share and per share data).

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