Interchangeability on the Ground in the First Island Chain
Across the Pacific, the clouds of Great Power Conflict are becoming harder to ignore. Beijing’s military expansion, the growing reach of its surveillance and strike systems, and its ability to disrupt allied logistics are forcing the United States and Australia to prepare for the possibility that they may be called to fight side by side as allies along the First Island Chain.
The 2026 U.S. National Defense Strategy and Australia’s 2026 National Defence Strategy reflect this emerging reality.[1][2] Both emphasize deterrence by denial, stronger allied contributions, resilient defence-industrial capacity, and forces capable of fighting and surviving inside a contested theatre.[3] Strategic alignment, however, is only the beginning. The real test is whether our forces can sustain one another once the fight begins.
In a recent conversation, Australian Major General Mick Ryan described the operational challenge to me directly: in a Pacific war, allied forces may have to ‘fight our way to the theatre.’ Once there, if ‘fight tonight’[4] is the standard, the first requirement is to ‘survive tonight.’[5]
For the United States and Australia, achieving that level of survivability – and, of course, lethality – cannot depend on separate, parallel national logistics chains.[6] It requires an integrated sustainment architecture built around industrial comparative advantage and mutual support. As I previously argued, the modern battlespace requires a move from allied interoperability to operational interchangeability: the ability to draw upon one another’s ammunition, maintenance, medical support, and sustainment across the combined force under fire.
To realise full interchangeability, consider the following recommendations – beginning with legislation. Ryan told me, ‘The issue is structural: U.S. rules are often laws; ours are policies. If we mess up, it’s a policy violation. If you mess up, you can go to jail or lose promotion – that’s a huge disincentive to share.’
Nevertheless, the challenge should not be considered insurmountable; the Department of War (DOW) has, over the years, worked closely with lawmakers to bring about legal pathways to increase acquisition speed and tear down existing barriers to engaging industry. One clear example is Congress’ extension of Other Transaction Authority to the Joint Force, adapting a flexible acquisition mechanism first granted to NASA in order to engage with industry at the speed of innovation – significantly reducing barriers and increasing the Department’s ability to rapidly field prototypes.[7]
Similarly, Washington’s need to deepen cooperation with Canberra led DOW and Congress to address statutory and regulatory barriers surrounding nuclear powered submarines, arguably one of the most closely protected capabilities in the American arsenal. The 2024 National Defense Authorization Act provided the legal foundation for an integrated AUKUS submarine enterprise, authorizing the transfer of three Virginia-class submarines to Australia and enabling the maintenance and industrial cooperation necessary to make the transfer operational.[8] These precedents demonstrate that although legal and policy barriers might exist, intragovernmental cooperation can create the necessary legal authorities to manage risk and leverage industrial opportunities when strategic defence requires it.
Legislation focused on interchangeability could yield great value and unleash the full magnitude of the US and Australian defence industrial base.
In practice, interchangeability has to begin before contract award, with American and Australian requirements communities identifying where common manufacturing standards, maintenance concepts, and sustainment architectures are actually needed. As Australian Air Vice-Marshal Andrew Dowse AO and his colleagues at RAND have argued, requirements cooperation creates the opportunity to align investments and deliberately build complementary capabilities rather than discover incompatibilities after systems are fielded.[9]
Acquisition authorities should also think through how to share access to the technical data and intellectual property necessary to sustain those systems.[10] Consider this plausible, tactical-level scenario along the First Island Chain: an Australian fabrication team working alongside Marines cannot produce a replacement part simply because the technology exists. Rather, the team must first possess the data rights necessary to maintain, repair, modify, or even reproduce what they expect their forces to support together. U.S. acquisition regulations already distinguish among unlimited, government purpose, and limited rights in technical data along with the installation maintenance procedures.[11] Interchangeability should thus be a consideration when technical-data deliverables and associated license rights are defined and negotiated, rather than an issue discovered under threat.
Policy and law should enable what strategy demands. AUKUS has already made meaningful progress: ITAR §126.7 framework now exempts lengthy export licensing processes on many eligible defence transfers among authorized U.S., Australian, and British users, although some excluded technologies and other restrictions remain.[12] AUKUS’ Pillar II is likewise moving toward shared standards, common control systems, and eventually joint development and production.[13] But export control is only one layer to consider. The larger challenge is whether allied personnel can actually access the classified information and technical data rights required to sustain one another’s systems. Where those barriers exist, departments should remove what they can and Congress should address what they cannot. Restrictions that prevent allied sustainment in peacetime will not become less consequential once the shooting starts.
The Department of War is already taking the necessary steps to make cooperation and eventual interchangeability possible.
In 2024, the Office of the Secretary of Defense established the Regional Sustainment Framework to facilitate maintenance, repair, and operations with our partners.[14] For allies, this is also where interchangeability becomes real, determining whether two forces can support one another in a fight. According to Dowse and his colleagues, ‘Cooperating when setting requirements instigates discussions that help align strategic objectives from the outset and ensure that national investment decisions contribute to a coherent allied force posture.’[15]
Taken together, my posts on the AARC Land Power Forum collapse into a single argument: mateship provides the trust to fight together, modernisation builds the capability, and interchangeability turns both into endurance under fire. If the United States and Australia expect to deter through denial – and, if necessary, fight together in the Pacific – we must learn how to develop, manufacture, operate, and sustain together closely enough that we are able to keep one another in the fight.
- Part 1: Mateship Under Pressure
- Part 2: Modernizing for Denial
- Part 3: Diggers and Leathernecks
Endnotes
[1] U.S. Department of Defense, 2026 National Defense Strategy (Washington, DC: Department of Defense, January 2026), https://media.defense.gov/2026/Jan/23/2003864773/-1/-1/0/2026-NATIONAL-DEFENSE-STRATEGY.PDF
[2] Australian Government, Department of Defence, 2026 National Defence Strategy and 2026 Integrated Investment Program (Canberra: Department of Defence, 2026), https://www.defence.gov.au/about/strategic-planning/2026-national-defence-strategy-2026-integrated-investment-program
[3] Robert Rushby, “Deterrence by Denial,” Sea Power Centre–Australia, accessed August 25, 2026, https://seapower.navy.gov.au/deterrence-denial
[4] Paul Gillikin, “‘We Fight Tonight’: Corps Capabilities for a Contested Indo-Pacific,” Seapower, April 25, 2025, https://seapowermagazine.org/we-fight-tonight-corps-capabilities-for-a-contested-indo-pacific/
[5] Maj. Gen. Mick Ryan, conversation with author, April 2, 2026.
[6] Johannes Schmidt, “Expeditionary Medical Systems: Increasing Warfighter Survivability in Littoral Combat,” U.S. Navy, December 28, 2023, https://www.navy.mil/Press-Office/News-Stories/Article/3627576/expeditionary-medical-systems-increasing-warfighter-survivability-in-littoral-c/
[7] Thomas J. Darmofal, “A Brief Overview of Other Transactions Authority,” Army Lawyer, 2025 Issue 2, July 16, 2025, https://www.lineofdeparture.army.mil/Journals/Army-Lawyer/Archive/Issue-2-2025/Other-Transactions-Authority/; 10 U.S.C. § 4022.
[8] National Defense Authorization Act for Fiscal Year 2024, Pub. L. No. 118-31, div. A, title XIII, §§ 1352–1353, 137 Stat. 136, 514–24 (2023); Australian Government, Department of Defence, “Passage of Priority AUKUS Submarine and Export Control Exemption Legislation by the United States Congress,” media release, December 15, 2023, https://www.minister.defence.gov.au/media-releases/2023-12-15/passage-priority-aukus-submarine-export-control-exemption-legislation-united-states-congress.
[9] Andrew Dowse, Daniel Marns, Austin Wyatt, Sachini Kadaoluwa, Megan McKernan, Stephen M. Worman, and Lucia Retter, Optimizing Defense Requirements Cooperation Among the United States and Its Allies, PE-A3510-1 (Santa Monica, CA: RAND Corporation, 2026), https://doi.org/10.7249/PEA3510-1
[10] U.S. Government Accountability Office, Weapon System Sustainment: DOD Can Improve Planning and Management of Data Rights, GAO-25-107468 (Washington, DC: Government Accountability Office, September 2025), https://www.gao.gov/assets/gao-25-107468.pdf
[11] Office of the Under Secretary of Defense for Acquisition and Sustainment, Intellectual Property Guidebook for DoD Acquisition (Washington, DC: Department of Defense, April 30, 2025), https://www.acq.osd.mil/asda/dpc/api/docs/intellectual%20property%20guidebook%20for%20dod%20acquisition%20signed.pdf
[12] U.S. Department of State, “International Traffic in Arms Regulations: Exemption for Defense Trade and Cooperation Among Australia, the United Kingdom, and the United States,” proposed rule, 89 Fed. Reg. 35028 (May 1, 2024), https://www.federalregister.gov/documents/2024/05/01/2024-08829/international-traffic-in-arms-regulations-exemption-for-defense-trade-and-cooperation-among
[13] Luke A. Nicastro, AUKUS Pillar 2 (Advanced Capabilities): Background and Issues for Congress, Congressional Research Service Report R47599 (Washington, DC: Congressional Research Service, May 21, 2024), https://www.congress.gov/crs-product/R47599
[14] U.S. Department of Defense, “Department of Defense Announces the Regional Sustainment Framework,” news release, May 15, 2024, https://www.war.gov/News/Releases/Release/Article/3776541/department-of-defense-announces-the-regional-sustainment-framework/
[15] Andrew Dowse et al., Optimizing Defense Requirements Cooperation Among the United States and Its Allies (Santa Monica, CA: RAND Corporation, May 2026), 3, https://www.rand.org/pubs/perspectives/PEA3510-1.html
