Missiles and multipolarity: Can an Indo-Pacific coalition defeat China’s missile overmatch?

Executive summary

• The United States and US-aligned states are facing generational geostrategic challenges in the Indo-Pacific from increasingly assertive and capable revisionist powers in China and North Korea.
• Facing these challenges, capable and like-minded regional democracies — namely Japan, Australia, South Korea, Taiwan, and the United States (JASTU) — are seeking to strengthen deterrence through the development of integrated air and missile defence (IAMD) capabilities.
• The development of these capabilities is currently being outmatched by Chinese advantages in scale and logistics. China’s ability to produce large volumes of air and missile systems at relatively low cost makes it unlikely that any one Indo-Pacific state acting in isolation can achieve the capability required to effectively defend against a massed Chinese air and missile strike.
• JASTU partners should, therefore, explore the force-multiplying effects of coalition-style operational coordination of IAMD, for example in terms of layering assets, establishing divisions of labour, and deconflicting engagements, i.e., ‘Coalition IAMD’. Coalition IAMD offers several theoretical benefits, including asset and capability aggregation, increased effective magazine depth, the distribution of risk, an expanded geographic scope for operations, and operational resilience and redundancy, each of which has the potential to strengthen deterrence.
• In June 2025, the United States Studies Centre (USSC) convened a Tabletop Exercise (TTX) in Honolulu, Hawaii with 20 Track 2 IAMD experts from military, industry, and academic backgrounds. The goal of the TTX was to establish realistic operating concepts for JASTU Coalition IAMD and to assess their potential utility in countering regional air and missile threats.
• The TTX exposed the upper limits of JASTU Coalition IAMD in the Indo-Pacific. Forward deploying ground-based assets on foreign territory, engaging red (hostile) targets vectored for a coalition state, or integrating fire control across partners were all seen as politically challenging under current conditions.
• However, the TTX indicated that there are Coalition IAMD operating concepts that are both operationally advantageous and politically feasible for near-term Indo-Pacific contingencies. These included:
  – ‘Latent Link’: Maintaining a cross-partner track-sharing capability that can be rapidly activated at the outset of a kinetic conflict. Latent Link involves building interoperable networks of IAMD assets such that coalition sensors and shooters can share fire-quality track data when needed.
  – ‘Long Sense/Short Defence’: Local point defence through layered high- and low-cost-per-engagement effectors with coalition partners providing sensing in depth. The partner under attack focuses on defending its own territory with cost-effective and high-end systems, while coalition partners contribute long-range and mobile sensors to deliver early warning, track sharing, and redundancy.
• While such coalition approaches to IAMD are unlikely to independently correct the Indo-Pacific air and missile balance, they can slow China’s widening of the air and missile gap in the short term while laying the groundwork for more ambitious operational integration of JASTU IAMD in the future.
• Opportunities for deeper Coalition IAMD are likely to increase as JASTU converge around the urgency of the China threat. This justifies continued interrogation of the case for Coalition IAMD.

The Indo-Pacific air and missile problem

Stability in the Indo-Pacific is under pressure from increasingly assertive and capable revisionist powers in China and North Korea. Capable and like-minded regional democracies — namely Japan, Australia, South Korea, Taiwan and the United States (JASTU)¹ — have sought to prevent Chinese and North Korean attempts to militarily revise the status quo through bolstering deterrence. Efforts to bolster deterrence have included the development of Integrated Air and Missile Defence (IAMD) capabilities, with high-profile examples including South Korea’s formation of a strategic command covering air and missile defence, Japanese development of two Aegis-equipped ballistic missile defence (BMD) cruisers, and the United States’ 2024 announcement of its intent to deploy additional Patriot missile batteries to the Indo-Pacific.

Stability in the Indo-Pacific is under pressure from increasingly assertive and capable revisionist powers in China and North Korea.

While these efforts have been significant, they are struggling to keep pace with the air and missile threat posed by China and North Korea. China, in particular, is undertaking rapid military expansion underpinned by a vast defence industrial base capable of producing large quantities of offensive air and missile systems at relatively low cost, as well as by internal lines of communication and logistics that enable the rapid forward deployment of these systems in likely Indo-Pacific contingencies. This capability threatens to overwhelm JASTU air and missile defences in a regional contingency. To bolster deterrence, therefore, JASTU must pursue new approaches to IAMD that offset relative Chinese advantages in scale and logistics.

While JASTU are politically and militarily connected through the US Indo-Pacific hub-and-spokes system, there are also growing threads of ‘spoke-to-spoke’ military-political cooperationSource: Australian Department of Defence

One approach involves operational coordination across JASTU. While JASTU are politically and militarily connected through the US Indo-Pacific hub-and-spokes system, there are also growing threads of ‘spoke-to-spoke’ military-political cooperation,² for example the 2023 Australia-Japan reciprocal access agreement, the commencement of Japan-Taiwan joint coast guard drills in 2024,³ and Australian and South Korean commitments to “strategic and security cooperation” under a 2021 ‘Comprehensive Strategic Partnership.’⁴ These burgeoning connections, along with Japan, Australia, South Korea, and Taiwan’s existing, deep bilateral engagements with the United States, provide a basis for coalition-style operational coordination of IAMD, for example in terms of layering assets, establishing divisions of labour, and deconflicting engagements — hereafter ‘Coalition IAMD’. ‘Coalitions’ need not be treaty allies, nor even have official relations (as many states do not with Taiwan). Rather, they are simply political collectives that engage in some degree of military coordination, often informally and in the context of a specific military crisis.⁵

Coalition IAMD offers several theoretical benefits that have the potential to offset China’s air and missile advantages, including asset and capability aggregation, increased effective magazine depth, the distribution of risk, an expanded geographic scope for operations, and operational resilience and redundancy.⁶ At the same time, there are enduring political challenges between the JASTU partners that are likely to place upper limits on the scale and scope of IAMD coordination. These include the limited institutionalisation of cooperative defence arrangements beyond the US hub-and-spokes, sometimes fractious bilateral relations, and diverging risk tolerances vis-à-vis China and the associated challenges in standardising rules of engagement (ROEs).⁷ This leaves two questions for JASTU planners considering coalition-based options for strengthening IAMD and, by extension, deterrence in the Indo-Pacific: How might Coalition IAMD realistically function in the Indo-Pacific? And what benefits might such coordination bring in countering regional air and missile threats?

How this report is structured

To answer these questions, in June 2025, the United States Studies Centre (USSC) convened a tabletop exercise (TTX) on Coalition IAMD in Honolulu, Hawaii, with Track 2 representation from JASTU.⁸ The TTX involved 20 IAMD experts working in groups to construct realistic IAMD architectures involving JASTU assets under a variety of Indo-Pacific contingencies. These architectures were analysed for recurring patterns to infer Coalition IAMD operating concepts, i.e. how JASTU might jointly operate IAMD in a conflict.

This report presents the findings from that exercise, outlining a set of Coalition IAMD operating concepts that participants judged to be both operationally advantageous and politically feasible for near-term Indo-Pacific contingencies. In doing so, this report makes two primary contributions to the policy and practice of Indo-Pacific defence coordination and IAMD. First, it presents JASTU Coalition IAMD as a viable option for stemming the dire air and missile balance in the Indo-Pacific. This should encourage further thinking and policy development around cross-jurisdictional options to strengthen air and missile defence in the face of rising revisionist threats, both in the Indo-Pacific and elsewhere. And second, it suggests operating concepts for JASTU Coalition IAMD, providing a framework for policy development and technology modernisation to direct JASTU efforts in strengthening operational IAMD coordination and deterrence.

This report proceeds in four stages. First, it introduces the challenges of deterrence and IAMD in the Indo-Pacific and positions Coalition IAMD as an option for mitigating these challenges. Second, it describes the TTX and how it was designed to explore credible operating concepts for Coalition IAMD across JASTU. Third, it presents the outcomes of the TTX in the form of two operating concepts that emerged from discussions: Latent Link and Long Sense/Short Defence. And finally, it offers concluding remarks on the future of Coalition IAMD.

Chinese People’s Liberation Army (PLA) soldiers fire a rocket into the air as they conduct military drills on Pingtan island, in eastern China’s Fujian province, the closest point to Taiwan, on 30 December 2025.Source: Getty

The strategic context

Indo-Pacific democracies are facing generational geostrategic challenges. The first is a revisionist and increasingly assertive China, which is aggressively postured around Taiwan, advancing multiple disputed territorial claims in the East and South China Seas, and engaging in a massive and opaque build-up of its conventional and nuclear forces. The second is an increasingly capable North Korea that is using its illicit nuclear and missile programs to coerce its neighbours and undermine US military commitments in the region.

Facing these challenges, the Indo-Pacific democracies have converged around ‘deterrence’ as an ordering principle of their respective defence strategies (Table 1). Taiwan’s 2025 Quadrennial Defense Review, for example, identified in the Minister’s preface Taiwan’s need to “integrate the full strength of the nation to build a multilayered deterrence capability.”⁹ And Japan’s 2022 National Defense Strategy lists as the second of Japan’s three ‘defense objectives’ the “deter[rence], through cooperation with our ally, like-minded countries and others, [of] unilateral changes to the status quo by force and such attempts that concern Japan’s peace and security.”¹⁰

As deterrence assumes an increasingly central role across JASTU strategy, so too has IAMD. IAMD serves a two-pronged role in deterrence. First, it bolsters ‘deterrence by denial’: deterring military aggression by reducing the likelihood that an adversary will achieve its objectives. IAMD intercepts of hostile air and missile systems limit damage to the defending force, requiring adversaries to either abandon the attack or expend more of their air and missile stockpiles to generate comparable military effects. Such overcommitments of air and missile assets both drain adversaries’ limited stockpiles and make the attacks more escalatory, imposing greater risks on launching them in the first place. And second, IAMD bolsters ‘deterrence by punishment’: deterring military aggression by ensuring costly retaliation. Blunting adversaries’ air and missile attacks on blue (friendly) military targets (ground-based missiles, forward operating bases, etc.) gives coalition or ‘blue’ states the time to launch, disperse, or harden protections for those assets. This gives blue states the strategic space to launch retaliatory strikes and maximise force readiness in response to adversaries’ first strikes. The result is, as put by missile defence expert Ankit Panda, that “Any military force planning long-range missile strikes will need to plan around the possible effects of missile defences.”¹⁶

The importance of IAMD in credible and effective deterrence is widely recognised. NATO, for example, has recently identified IAMD as “an essential element of NATO’s deterrence and defence posture, contributing to the Alliance’s indivisible security and freedom of action, including NATO’s ability to reinforce its deployments and to provide a strategic response.”¹⁷ JASTU, seemingly sensitive to this logic, are increasingly investing in IAMD capabilities to bolster their respective deterrence postures. The United States and Taiwan are, for example, advancing concepts for homeland air and missile defence based on Israel’s nation-wide Iron Dome system (Golden Dome and T Dome, respectively);¹⁸ South Korea is developing an indigenous air defence system for North Korean long-range rocket and artillery attacks;¹⁹ Japan is codeveloping with the United States a Glide Phase Interceptor (GPI) for hypersonic missiles;²⁰ the United States is planning a four-fold increase in procurement of PAC-3 Missile Segment Enhancement (MSE) interceptors;²¹ and Australia, in response to what its 2023 Defence Strategic Review described as an “urgent” need for “layered integrated air and missile defence,”²² is investing in airborne early warning, battle management, and Over-the-Horizon (OTH) radar (Table 2).

TABLE 2.
AUSTRALIAN GOVERNMENT INVESTMENTS IN MISSILE DEFENCE (AUD)²³

While each JASTU partner is making significant IAMD investments, deterring aggression, especially vis-à-vis China, is still likely to be an uphill battle. China has two advantages in terms of the regional air and missile balance. The first is its unique ability to generate a mass of fires due to: (a) its massive missile and unmanned aerial system (UAS) stockpiles, (b) its sprawling defence industrial base capable of rapidly replenishing these stockpiles, and (c) its interior lines of communication allowing it to rapidly deploy these assets to the front lines of likely conflict scenarios, i.e. the ‘homefield advantage.’²⁴ This mass of air and missile threats is likely to rapidly exhaust JASTU’s limited stockpile of air and missile interceptors in a conflict. Recent modelling from the Stimson Centre, for example, found that “the United States would likely run out of Patriot and THAAD interceptors within the first 24 hours of a military conflict” in the Indo-Pacific.²⁵

This ‘magazine depth’ issue is compounded by China’s ability to generate mass at low cost. In addition to its exquisite air and missile systems, including hypersonics and anti-ship ballistic missiles, China fields several high-volume, low-cost systems.²⁶ China’s deployment of massed, low-cost UAS and missiles has the potential to impose unfavourable cost ratios upon competitors as multiple interceptors with unit costs as high as tens of millions of US dollars are expended on single targets that are 10–100 times cheaper and quicker to produce. In the 12-day Iran-Israel conflict in June 2025, for example, the United States expended 100–150 THAAD (Terminal High Altitude Area Defense) interceptors against Iranian medium-range ballistic missiles (MRBMs). This amounted to approximately 25% of the US stockpile — or up to 150% of annual global production — at a cost ratio of approximately ten-to-one (favourably assuming only one interceptor per missile).²⁷

These interrelated challenges of magazine depth and cost-per-engagement lay bare the risks of JASTU pursuing IAMD independently. While regional democracies may previously have favoured independent approaches to IAMD, for example to maximise autonomy in decision making or prevent entrapment in allied air and missile conflicts,²⁸ it is now unlikely that any one Indo-Pacific jurisdiction acting in isolation can achieve the capability required to effectively defend against a massed Chinese air and missile strike — especially amidst competing spending priorities and already overstretched defence industrial bases.²⁹

The Indo-Pacific is a unique theatre, distinct in both politics and geography from Europe and NATO, with limited institutionalisation of JASTU cooperative defence arrangements beyond the US hub-and-spokes and extreme distances separating these potential IAMD partners.

In closing the air and missile gap with China, JASTU must therefore consider the force-multiplying effects of a coalition-style operational coordination of IAMD — or ‘Coalition IAMD’ — in terms of layering assets, establishing divisions of labour, and deconflicting engagements. Recent analyses point to the potential benefits of Coalition IAMD, for example in terms of asset and capability aggregation, increased effective magazine depth, the distribution of risk, an expanded geographic scope for operations, and operational resilience and redundancy, particularly in the NATO context.³⁰ The application of such a model in the Indo-Pacific has the potential to offset China’s air and missile advantage, bolstering deterrence in the Indo-Pacific.

The applicability of this NATO model in the Indo-Pacific is, however, uncertain. The Indo-Pacific is a unique theatre, distinct in both politics and geography from Europe and NATO, with limited institutionalisation of JASTU cooperative defence arrangements beyond the US hub-and-spokes and extreme distances separating these potential IAMD partners. Any considered treatment of Coalition IAMD in the Indo-Pacific must therefore begin with an examination as to how Coalition IAMD might realistically function in this theatre and what military benefits, if any, might accrue in countering regional air and missile threats.

Developing JASTU IAMD operating concepts through TTX

In June 2025, the USSC convened a TTX on Coalition IAMD in the Indo-Pacific. The goal of the TTX was to establish realistic operating concepts for JASTU Coalition IAMD and to assess their potential utility in countering regional air and missile threats. We approached this through an exercise in force design. Specifically, we recruited experts in IAMD and tasked them with working in groups to construct realistic IAMD architectures involving JASTU assets under a variety of Indo-Pacific contingencies. We then analysed these architectures for recurring patterns to infer how JASTU might jointly operate in a conflict.

The goal of the TTX was to establish realistic operating concepts for JASTU Coalition IAMD and to assess their potential utility in countering regional air and missile threats.Source: Getty

This process began by recruiting four ‘players’ from each JASTU partner to attend the TTX (20 total, all Track 2). All players were experts in IAMD, drawn primarily from military, industry, and academic backgrounds. At the TTX, players were divided into four groups of five, with each group having exactly one player from each JASTU jurisdiction. Players were presented with a hypothetical IAMD scenario involving a Chinese air and missile attack in the Indo-Pacific (the scenario was the same across teams). Each scenario included a map with the locations of key red (Chinese) and blue (JASTU) assets, as well as a narrative description of how the scenario unfolded, for example, which units attacked which units in what order, which forces were damaged and how, etc. (see Figure 1). Players were then instructed to construct an IAMD architecture to “stop this from happening.” In other words, players were charged with constructing an IAMD architecture that, had it been in place at the moment of the attack, would have minimised damage to blue forces and infrastructure and denied the attacking Chinese forces their operational objectives to the greatest extent possible. In constructing their architectures, players were able to procure assets under the operational authority of Japan, Australia, South Korea, Taiwan, or the United States. Each of these five partners received a budget of game ‘points’ with which to purchase capabilities. A long-range active electronically scanned array (AESA) search radar, for example, cost five points, a cannon-based short-range air defence (SHORAD) system cost two points, etc.

Source: USSC

FIGURE 1.
SCENARIO 1: A CHINESE DRONE AND CRUISE MISSILE ATTACK ON YONAGUNI

Importantly, purchase decisions were not made unilaterally. The player from South Korea, for example, did not choose unilaterally what South Korea would purchase for the architecture. Instead, teams were instructed to function as a multinational task force that made collective recommendations regarding purchases across JASTU.

Each purchase recommendation needed to include: (a) the system that was purchased (and for how many points), (b) where it was placed in theatre, and (c) how (if at all) it was integrated with other in-theatre assets. For example, a team may have recommended that Japan purchase (a) an Airborne Early Warning (AEW) system for five points, (b) have it patrolling the Ryukyu islands, and (c) feed sensor data to in-theatre Japanese and US assets through Link 16.

Teams faced three constraints in making these recommendations. First, there were upper limits as to how many points each partner had to make purchases (typically five). Second, teams could only make recommendations that they judged were politically realistic.

TABLE 3.
AIR AND MISSILE DEFENCE SCENARIOS IN THE TTX

Specifically, they were instructed to make recommendations only if they judged that those recommendations would have a ‘better than even’ chance of being adopted across all five partners under prevailing political conditions. And third, teams were sometimes restricted in terms of what systems they could purchase or how they could integrate them (Table 3). For example, in Scenario 3, Team 2 could not purchase unmanned aerial systems (UASs), including HALE and MALE (high- and medium-altitude long-endurance), Unmanned Combat Aerial Vehicles (UCAVs), and UAS/UHF (Ultra High Frequency) relay systems. Doing so simulated decision-making across a variety of strategic futures. For example, the inability to purchase certain systems simulated futures in which supply chain shortages, stringent export controls, or underinvestment in emerging technologies restricted the availability of these systems. This provided analytical leverage in assessing (a) the impact of these constraints on IAMD architectures, and (b) the robustness of the findings across a variety of strategic futures.

The above process was repeated four times for four discrete scenarios: (1) a Chinese drone and cruise missile attack on Yonaguni; (2) a Chinese, multi-vector attack on multiple sites in the Ryukyu Islands; (3) a Chinese, multi-vector attack on Palawan and nearby blue team naval forces; and (4) a Chinese, long-distance bomber raid on Darwin. All four scenarios were judged to be extreme, but realistic in the near term in the context of a Chinese, theatre-wide campaign. The scenarios also simulated magazine depth and cost-per-engagement challenges. Existing in-theatre blue team assets often presented as ‘Winchester’ (out of ammunition) or without sufficient volumes of effectors. And scenarios often began with attacks of low-cost drones and missiles designed to saturate high-cost blue team interceptors.

JASTU is not NATO, and there are enduring political and geographic impediments that place upper limits on the scope and scale of operational IAMD coordination, even in challenging geostrategic circumstances.

The above process yielded 16 discrete IAMD architectures involving JASTU assets and tailored to various Indo-Pacific contingencies and constraints. Analysis of those architectures was undertaken to identify recurring patterns of JASTU operational IAMD coordination, which were then formalised into a series of Coalition IAMD operating concepts (detailed in the following section). Importantly, the goal of this exercise was not to furnish a series of Coalition IAMD operating concepts that were necessarily comprehensive or novel in military terms, or unique to JASTU. Nor was it to ‘prove’ or ‘validate’ these concepts. Instead, this was an exploratory exercise in the ‘art of the possible’ in coordinated approaches to IAMD. This TTX sought to develop experimental Coalition IAMD operating concepts to spur thinking about coalition-based options for managing growing air and missile threats, and to advance frameworks for policy development, technology modernisation, and industrial capability that provide JASTU opportunities to exercise these options.

Principles of TTX design

Before proceeding, it is worth underscoring the three principles that drove the design of this TTX and that, consequently, underpin the findings discussed below. First, this TTX was principally concerned with identifying options for the operational coordination of JASTU IAMD. That is, at the level of military operations, in terms of layering assets, establishing divisions of labour, and deconflicting engagements in a theatre-level conflict. This is not to suggest that there are not promising options for coordinating JASTU IAMD ‘upstream’ of operations, for example in terms of IAMD strategy, logistics, procurement, or research and development. Such matters are, however, out of scope for the present analysis.

Second, we designed the TTX to promote integrative solutions to Indo-Pacific air and missile threats across JASTU. While a great deal of planning and intellectual development informs IAMD force design at the national level, through this TTX, we pushed players to consider solutions to air and missile threats that involved operational coordination across JASTU. We did this by constructing teams that included equal representation from all five partners; assigning each partner points to spend in each of the scenarios; and using scenarios that were likely to overstretch partners acting in isolation, forcing players to weigh the force-multiplying effects of the coordination of IAMD across partners.

And third, we designed this TTX to provide realistic options for Coalition IAMD. JASTU is not NATO, and there are enduring political and geographic impediments that place upper limits on the scope and scale of operational IAMD coordination, even in challenging geostrategic circumstances. Analysis that has policy relevance must, therefore, temper military-technical arguments which are likely to favour the force-multiplying effects of close-knit integration with political realities that bound what can realistically be achieved in the near term.³¹ We incorporated these considerations into the TTX by requiring that players make recommendations regarding JASTU IAMD architectures not just with respect to military considerations of harm minimisation and cost-effective defence, but also with respect to the likelihood of political support for the architectures.

Coalition IAMD operating concepts

Operating concepts (also known as ‘operational concepts’) are “generic scheme[s] of maneuver” that describe, at a theatre level, how military assets will be used to prevail in a particular type of engagement.³² The Air-Land Battle concept employed by the United States in the 1980s, for example, was structured around conflicts with a quantitatively superior opponent, and emphasised close-air support to front-line troops coupled with strikes behind enemy lines to degrade the enemy’s front-line offensive.³³ In the IAMD context, operating concepts are principally concerned with the placement and integration of networks of sensors and shooters, and their ROEs with red team assets in a given scenario.

Following the procedure detailed in the previous section, the TTX generated 16 IAMD architectures involving JASTU assets positioned to defend against various Chinese air and missile attacks under various constraints. The authors analysed these architectures to identify recurring patterns of JASTU operational coordination, which were then formalised into a series of Coalition IAMD operating concepts. Below, we detail the two operating concepts that emerged from the TTX: (1) Latent Link, and (2) Long Sense/Short Defence.

Latent Link

IAMD ‘battle management’ involves the networking of sensors and shooters within an area of operations. Instead of clusters of sensors and shooters operating in isolation, battle management connects all sensors and shooters across the entire theatre, effectively allowing them to ‘talk to eachother.’

At a national level, IAMD battle management offers several advantages. Shooter access to more track data (i.e. from multiple sensors) can improve battlefield awareness, early warning, cueing, and the fidelity of tracks, improving shooter performance. Having multiple, networked sensors closes gaps in coverage and provides redundancy against the failure or loss of individual sensors. And integrating shooters supports inventory management as command can more optimally assign its full range of effectors against individual targets. This theoretically reduces the incidence of: commands uneconomically expending high-cost effectors on low-value targets; blue overkill, where multiple effectors are unnecessarily assigned to the same target; or blue-on-blue incidents in congested areas of operation.

Within the TTX, the demand for battle management at the level of individual jurisdictions was strong: more in-game points were expended on battle management than for any other capability. Interestingly, players also explored how jurisdiction-level battle management systems could be integrated across JASTU. Players reasoned that networking jurisdiction-level battle management systems in this way would supercharge the abovementioned advantages of battle management (inventory management, early warning, etc.), i.e. by increasing the supply and geographic distribution of sensors and shooters.³⁴

These discussions centred on integrating a specific function of battle management, namely track sharing. Overall, there was consistent demand for cross-jurisdictionally integrated track sharing. That is, players consistently recommended networking all in-theatre coalition assets (i.e. across JASTU) such that all sensors could feed track data to all shooters (i.e. both within and across partners), whether through the procurement and integration of dedicated battle management systems, or through Link 16, or both. In Scenario 1, for example, all teams that were not restricted from doing so incorporated this cross-partner track sharing capability into their architectures.

As the vignettes progressed and became more complex, the demand for cross-partner track sharing only grew stronger. Even facing financial constraints and higher volumes of air and missile threats that created pressures to procure more effectors, teams consistently prioritised track sharing through the procurement and cross-partner integration of dedicated battle management systems (see, for example, Figure 2). Indeed, in team discussions, establishing such track-sharing arrangements was typically viewed as the ‘start point’ for architecture design. This demonstrated an operational emphasis on countering air and missile threats through improving the performance and effectiveness of existing in-theatre shooters, i.e. through cross-partner track sharing and the associated gains in tracking, targeting, redundancy, inventory management, cueing, and early warning.

Source: USSC

FIGURE 2.
TEAM 1'S COALITION IAMD ARCHITECTURE FOR DEFENDING AGAINST AN ATTACK ON OKINAWA

Political considerations

When challenged on the political feasibility of sharing track data between JASTU militaries, players consistently judged that any political constraints on sharing tracks between JASTU would “disappear into the distance” in the context of a kinetic regional conflict. One participant, for example, posited that “once Japan has been attacked by the PLA, then I think they can change their policy to share information with [Taiwan],” with another participant responding that “I would suggest that Australia would do the same… once the missile firing starts, I think there would have to be a rethink about sharing.”

Unlike integrating fire control (i.e. one partner targeting and launching another’s effectors) — which players judged to be politically infeasible, even in the context of a shooting war in the Indo-Pacific — track sharing through cross-partner, integrated battle management would allow partners to retain ultimate decision-making authority over the use of their own shooters: what one player described as a “sovereign opportunity to use shared data.”

The above support for cross-partner track sharing comes with one major caveat, however: it is contingent upon the existence of, or imminent threat of kinetic conflict. Under pre-conflict conditions, there was less certainty that JASTU would have the political will to share track data. This is problematic as the procurement, testing, training, and policy development around cross-partner track sharing takes time, particularly when such track sharing spans multiple services and militaries. The dilemma left for policymakers is that, by the time the operational need for cross-partner track sharing becomes urgent (i.e. once the shooting starts), it may be too late to put the requisite systems and agreements in place.

One solution to this dilemma is to begin putting in place the requisite systems and agreements now, but in a deactivated, or ‘latent’ form. For example, JASTU might integrate their IAMD assets within battle management systems at the national level — for example with the US Integrated Battle Command System (IBCS)³⁵ and the Australian Air6500 program³⁶ — and develop now the data and communications protocols for these partner-level systems to talk to each other. When the shooting starts and politics change, links between these compatible, partner-level systems can be ‘switched on’ to activate coalition track sharing.

The above suggests a credible Coalition IAMD operating concept — which we label ‘Latent Link’ — in which JASTU establishes a cross-partner track sharing capability that is ‘inactive’ in peacetime but can be activated at the outset of a kinetic conflict. Latent Link presents a promising operating concept for JASTU Coalition IAMD in that it is both politically ‘cheap’ and operationally advantageous. It is politically cheap in that track sharing is not active in peacetime, and in that it does not require delegating or sharing fire control to or with other partners. And it is operationally advantageous in that it provides partners with improved inventory management, battlefield awareness, early warning, cueing, track fidelity, and sensor redundancy in wartime.

Requirements

There are two primary capability requirements for Latent Link. The first is the capability to share fire-quality track data between platforms and partners. A 2019 US Army test of IBCS, for example, demonstrated such a capability when it merged data from multiple US sensors (F-35s and PATRIOT, Sentinel, and TPS-59 Radar) and services (US Army, Air Force, and Marine Corps) to track two cruise missile surrogates that were successfully intercepted with PATRIOT Advanced Capability-2 (PAC-2) missiles.³⁷ Australia’s Air6500 program is aiming for a similar capability through a ‘system-of-systems’ designed to connect “disparate ADF [Australian Defence Force] systems and platforms across all domains.”³⁸ The second capability requirement is that track-sharing links between partners’ sensors and shooters are regulated such that they are, by default, inactive but can be rapidly activated in wartime.

Latent Link also requires developments in JASTU policy. First, to create demand for, and seize the opportunities of track sharing between platforms and partners, JASTU partners must align their IAMD operational planning around fully integrated sensors and shooters, rather than clusters of sensors and shooters operating in isolation. At the jurisdiction-level, this is already policy in the United States and Australia with IBCS and Air6500, respectively. And Japan, South Korea, and Taiwan are advancing comparable concepts in Japan Aerospace Defense Ground Environment (JADGE),³⁹ Korea Air and Missile Defense (KAMD),⁴⁰ and “T-Dome,”⁴¹ respectively. Second, JASTU partners must prioritise procurement of interoperable platforms. While legacy systems are likely to require ‘translators’ such as those provided by IBCS and Air6500, next-generation IAMD systems may be designed to seamlessly plug into these open architectures. Third, agreements between JASTU partners that preapprove track sharing in a conflict must be sought such that track sharing can be activated at the outset of conflict at a speed of relevance.⁴² Fourth, JASTU partners must build interoperability and experience working in cross-partner IAMD operations through joint exercises.⁴³ And fifth, JASTU partners must establish their own policies regarding firing on tracks provided by partner militaries that take into account, for example, concerns around the comprehensiveness and fidelity of track data.

Long Sense/Short Defence

In constructing regional IAMD architectures, constraints on the forward deployment of assets often emerged. Players were heavily constrained in forward deploying ground-based assets on foreign territories, whether for legal or political reasons.⁴⁴ And players judged that jurisdictions would be constrained in forward deploying assets that they would otherwise need to keep close to the homeland in case the conflict escalated, with one player remarking that “You can’t expect the Japanese or the Koreans to send their limited assets that far away from home, because there’s always going to be a threat that the home islands are going to be attacked.” This exposed a dilemma for players: while partners may seek to strengthen deterrence in the Indo-Pacific by contributing to coalition force structures, their ability to do so through forward deployments of IAMD assets would likely be constrained. Teams engaged this problem by establishing a division of labour between (1) point defence, performed by the partner under attack; and (2) long-range sensing, performed by coalition partners not under direct attack.

Point defence

In the IAMD architectures recommended by players, the partner whose territory was being attacked would typically take charge of ground-based deployments for point defence. This was judged to be the most politically expedient as it would sidestep the above mentioned constraints on the forward deployment of ground-based assets on foreign territories.

Importantly, to get on the right side of the cost curve re cost-per-engagement issues, teams typically included in the point defence role low-cost-per-engagement shooters that could engage high-volume, low-cost threats (drone swarms, etc.) at proportionate cost, for example stinger missile, missile and cannon SHORAD, and microwave and laser systems. This allowed high-end systems such as F-35s and air warfare destroyers to reserve their limited effectors for advanced cruise and ballistic missile threats targeting critical assets.

Scenario 1, for example, involved a Chinese drone and cruise missile attack on the Japanese Island of Yonaguni (Figure 1). It began with a massed Chinese drone strike that degraded local defences, leaving the island vulnerable to a follow-up barrage of air-, land-, and sea-launched cruise missiles. Players were quick to point out that relying only on in-theatre, high-end shooters such as the Chu-SAM, DDGs, and F-15 would rapidly exhaust interceptor stockpiles.⁴⁵ This led discussions on defending Yonaguni to emphasise cost-effective SHORAD: “If you can handle the missiles or the drones coming in with a SHORAD system, then you’re not wasting AMRAAMs or SM6s or SM2s… This is important in this fight because you will run out in about six weeks. You’re going to run out of all of this stuff.”

Accordingly, teams consistently incorporated into their Scenario 1 point defence architectures ground-based, low-cost-per-engagement shooters on Yonaguni to counter the initial drone swarm and provide an additional layer of defence against the follow-up cruise missile strike. Team 1, for example, emplaced an M-SHORAD and microwave systems on Yonaguni Island (Figure 3). Doing so, it was reasoned, would keep the high-value, in-theatre assets, such as the Japanese Chu-SAM and F-15, safe and with sufficient inventory to respond to the follow-up cruise missile attack. When restricted from purchasing SHORAD assets, teams struggled to manage the drone swarm issue. Team 3, for example, was forced to reassign Chu-SAM and F-15 fires to the drones, which reduced the readiness and inventory of these high-end systems for managing the follow-up cruise missile attack.

Source: USSC

FIGURE 3.
TEAM 1'S ARCHITECTURE TO DEFEND YONAGUNI, DEPLOYING LOW-COST-PER-ENGAGEMENT SHOOTERS IN A POINT DEFENCE ROLE WITH MOBILE COALITION SENSORS PROVIDING DEPTH

Long-range sensing

JASTU partners not being attacked directly prioritised long-range and mobile sensors and relays that could either support coalition forces from their home territories, or could be rapidly recalled to their home territories, such as AEW, HALE and MALE, and various unmanned systems. For players, the advantage of acquiring these systems was that they could contribute to coalition force structures at low political cost, both because they were based in or could be readily recalled to their home territories, and because sensing/relay was seen as less politically problematic than shooting.

In Scenario 1, for example, Team 1 recommended that South Korea, the United States, and Australia acquire mobile surveillance systems to circle Yonaguni, providing redundancy to the vulnerable ground-based sensors on the island (Figure 3). In another example involving a Chinese bomber-led attack on Darwin (Scenario 4), Team 2 recommended that Japan, South Korea, Taiwan, and the United States all procure and deploy to the South China Sea airborne sensors — including two long endurance/relay UASs and an autonomous battle management UAS with relay — to provide early warning and feed tracks on the incoming bombers to regional coalition assets (Figure 4). This was critical for focusing Australian combat air patrols, which would otherwise struggle in the north of the country given limited inventory and the massive distances that they need to cover. Thus, even though Japan, South Korea, Taiwan, and the United States did not directly engage Chinese bombers or deploy assets to Darwin, which players judged would be politically challenging or operationally disadvantageous in the scenario, they were able to strengthen Australia’s defence of Darwin through early warning and track sharing with mobile sensors.

The above suggests a credible Coalition IAMD operating concept — which we label ‘Long Sense/Short Defence’ — centring on two elements. The first is that the partner under attack focuses on point defence through a combination of high- and low-cost-per-engagement effectors. The second is that other JASTU partners support point defence through mobile and long-range sensing that provides redundancy and early warning to point defence sensors.

As with Latent Link, Long Sense/Short Defence presents a promising operating concept for JASTU Coalition IAMD in that it is both politically cheap and operationally advantageous. It is politically cheap in that it does not require engaging air and missile threats vectored for other partners, the emplacement of IAMD assets on foreign territories, delegating or sharing fire control to or with other partners, or the long-term deployment of IAMD assets beyond the homeland. And it is operationally advantageous in that it provides partners with cost-effective point defence; improved battlefield awareness, early warning, cueing, and track fidelity; and sensor redundancy and depth. Indeed, the demand for early warning and sensing in-depth will only increase as China ramps up production and deployment of hypersonics,⁴⁶ the speed and flight altitude of which will require early detection and OTH sensing.

Source: USSC

FIGURE 4.
TEAM 2'S ARCHITECTURE TO DEFEND DARWIN, WITH MOBILE AND LONG-RANGE COALITION SENSORS TRACKING INBOUND CHINESE BOMBERS

Requirements

As with Latent Link, Long Sense/Short Defence hinges on the ability of JASTU partners to share fire-quality track data between their respective sensors and shooters. Therefore, the capability and policy requirements for Latent Link also apply to the Long Sense/Short Defence operating concept. In addition to these base requirements, the JASTU partner responsible for point defence in a Long Sense/Short Defence posture (i.e. the force element most likely to be targeted) will require two broad capabilities. The first is the capability to absorb an opening salvo of high-volume, low-cost air and missile attacks, specifically through low-cost-per-engagement systems with high magazine depth. Lasers, microwaves, and canon-based SHORAD present compelling options, with cost-per-engagement theoretically as low as “pennies per shot.”⁴⁷ The second is the ability to defend against those advanced threats vectored for high-value targets for which low-cost-per-engagement effectors might be ill-suited: hypersonics, submarine-launched ballistic missiles (SLBMs), etc. Here, partners will have a stronger strategic and economic case for utilising exquisite systems such as highly capable surface-to-air and air-to-air missiles (standard missiles, etc.) to intercept these threats.

Those JASTU partners not under direct attack but providing coalition long-range sensing support will require long-range and/or mobile sensing platforms, such as AEW aircraft, HALE UASs, and OTH radar installations that can feed early warning and track data on incoming threats to the point defence partner.

In terms of policy requirements, Long Sense partners must establish policies for pre-positioning and tasking long-range/mobile sensing assets for coalition vulnerabilities. Whereas Short Defence partners must establish ROEs that optimally assign high- versus low-cost-per-engagement effectors to a variety of threats. There will be multiple factors that bear on the economic assignment of effectors to threats, for example threat type, threat volume, threat target, interceptor inventories and supply lines, time-to-impact, and the political status of the conflict.

Lasers, microwaves, and canon-based SHORAD present compelling options, with cost-per-engagement theoretically as low as “pennies per shot.”Source: US Department of War

The future of coalition IAMD

The Indo-Pacific air and missile balance is increasingly turning against regional democracies, driven primarily by China’s rapid military expansion, vast defence industrial base, and interior lines of communication. The operational coordination of JASTU IAMD (Coalition IAMD) — in terms of layering assets, establishing divisions of labour, and deconflicting engagements — has the potential to yield benefits that offset China’s relative air and missile advantages, including asset and capability aggregation, increased effective magazine depth, the distribution of risk, an expanded geographic scope for operations, and operational resilience and redundancy. However, military-political coordination between JASTU is a fraught process, complicated by the limited institutionalisation of cooperative defence arrangements beyond the US hub-and-spokes, sometimes fractious bilateral relations, and diverging risk tolerances vis-à-vis China.

This report details the outcomes of a TTX designed to test the feasibility of the Coalition IAMD concept in the Indo-Pacific by bringing together IAMD experts from JASTU, exposing them to simulated air and missile contingencies, and charging them with producing JASTU IAMD architectures that are both operationally advantageous and politically realistic.

There are Coalition IAMD operating concepts that are both operationally advantageous and politically feasible for near-term Indo-Pacific contingencies.

The TTX exposed the upper limits of JASTU Coalition IAMD in the Indo-Pacific. Forward deploying ground-based assets on foreign territory, engaging red targets vectored for a coalition state, or integrating fire control across partners were all seen as politically challenging under current conditions. However, the TTX also indicated that there are Coalition IAMD operating concepts that are both operationally advantageous and politically feasible for near-term Indo-Pacific contingencies. Two such operating concepts furnished through this TTX — Latent Link and Long Sense/Short Defence — presented several advantages through which coalition assets operated as more than the sum of their parts, including improved battlefield awareness and track fidelity, improved early warning, and cost-effective short-range intercepts (Table 4).

Such coalition approaches to IAMD are unlikely to independently correct the Indo-Pacific air and missile balance: doing so will require major reforms across multiple dimensions, including technology, industry, logistics, and strategy. They do, however, have the potential to generate cross-partner IAMD efficiencies that mitigate China’s widening of the air and missile gap in the short term. They may also lay the groundwork for more ambitious operational IAMD cooperation, for example in terms of command and control, fire control, basing, and standardising/deconflicting ROEs. While such cooperation may seem politically infeasible now, it may become feasible over time as regional politics change. Indeed, trends in Indo-Pacific politics suggest that the opportunities for Coalition IAMD will only increase, including US demands for allied burden sharing,⁴⁸ military-political rapprochement between historically fraught bilaterals,⁴⁹ and a growing consensus regarding the urgency of the China threat.⁵⁰

Recommendations

Pushing the Coalition IAMD agenda forward requires a concerted effort between JASTU policy makers, militaries, industry, and academia. Policy makers should navigate the political challenges of closer military cooperation with JASTU partners to create an enabling policy environment for military planners to seize the operational advantages of Coalition IAMD.

Recommendations for JASTU policy makers:

• Integrate IAMD assets under jurisdiction-level battle management systems and establish now (in the pre-conflict phase) the capability to share track data with coalition partners through these respective systems.
• Prioritise the procurement of open architecture next-generation IAMD systems while pursuing minimum viable integration with legacy systems.
• Establish cross-coalition agreements for sharing fire-quality tracks, including provisions for data and communications protocols, intelligence sharing, and cyber security.

JASTU militaries should deploy their military expertise to identify opportunities and use cases for Coalition IAMD in military operations, workshop and refine these operating concepts, and build their own capacity to implement these operating concepts.

Recommendations for JASTU militaries:

• Promote military-to-military engagements that build fluency with respective IAMD systems and allow partner militaries to identify and seize opportunities for closer coordination.
• Workshop and wargame Coalition IAMD operating concepts with JASTU partners.
• Deploy advanced battlespace management systems through INDOPACOM that can provide a common operating picture and target acquisition priorities for commanders, and that can be tailored as policy, regulations and doctrine evolve in each JASTU jurisdiction.

JASTU industry should reduce barriers to interoperability between IAMD platforms and partners by designing and marketing next-generation systems for open architectures and coalition warfare.

Recommendations for JASTU industry:

• Prioritise the development of open architecture systems that can readily ‘talk to’ other IAMD systems in networked data architectures.
• Design and market next generation IAMD systems for their ability to ‘plug into’ Coalition IAMD architectures, for example in sharing fire-quality tracks or providing long-range sensing functions for coalition partners.
• Develop low-cost-per-engagement interceptors with high magazine depth for managing low cost/high volume air and missile threats.
• Develop mobile and long-range sensors that can track threats over the vast distances of the Indo-Pacific.

JASTU academics should continue to interrogate the case for Coalition IAMD where governments, militaries, and industry may be unwilling or unable due to political or capacity constraints.

Recommendations for JASTU academics:

• Lead public discussions and convene stakeholders to develop concepts, public awareness, and social license for Coalition IAMD.
• Test/validate the case for Coalition IAMD, for example by conducting military analyses that model the effects of Coalition IAMD on air and missile defence outcomes; or drawing lessons from historical cases of internationally coordinated IAMD, for example in NATO, Ukraine or the Middle East.
• Map opportunities and pain points in multilateralising air and missile defence, for example in terms of existing coalition force structures and joint training programs; supporting technologies and components at high technology readiness levels (TRLs) to facilitate rapid trialling of Coalition IAMD operating concepts; and opportunities to shape JASTU policy on Coalition IAMD through forthcoming defence strategies, investment and procurement plans, etc.

Acknowledgements