The US Military Munitions Depletion Crisis Triggered by the Iran War and Security Response Strategies for South Korea, Japan, and the Philippines

Executive Summary

As the Iran War has dragged on for more than five months, US precision-guided munitions such as ATACMS and PrSM have been almost entirely depleted, while THAAD interceptor missile stockpiles have fallen by at least 38% compared to pre-war levels. Patriot inventories have also declined by 65%, with recovery proceeding slowly. Because this depletion stems from strategic assets that had originally been deployed to deter China, Russia, and North Korea on other fronts, it has direct implications for the defense postures of South Korea, Japan, and the Philippines. Given the structural bottleneck whereby expanding defense production lines requires anywhere from several months to several years, the most realistic outcome is the baseline scenario (55% probability), in which US force deployment priorities remain tied down in the Middle East. Accordingly, South Korea should verify the availability status of THAAD assets and accelerate the early deployment of L-SAM; Japan should expand PAC-3 co-production; and the Philippines should establish EDCA contingency plans—each managing the resulting gap in the structure of dependence on the United States.

I. Situation Analysis of the Issue

The US Military Munitions Depletion Crisis in the Iran War: Situation Analysis

1. Background and Development of the Issue

As of August, the war that began on February 28, 2026, with Israeli and US airstrikes on Iran has exceeded five months in duration [10]. Contrary to the Trump administration's initial framing of a "short, decisive intervention," the situation on the ground has evolved into a protracted war of attrition [14]. The Tehran Times assessed that this had run into "an unprecedented wall of industrial projection capacity" [14].

It was confirmed through Defense News reporting in early August that the US Army's ground-launched precision strike weapons—namely ATACMS and PrSM—had been almost entirely depleted over the course of the war [4]. The Gulf Daily News, citing the same sources, likewise reported that "the US military has used virtually all of its long-range precision-guided munitions" [7]. Because these weapons were not originally designed for operations against Iran but rather constituted strategic assets held in reserve for other fronts such as China, Russia, and North Korea, the ripple effects of this depletion are substantial [4].

The pace of depletion on the air-defense side was even steeper. According to CSIS tallies, THAAD interceptor missile stockpiles fell from 452 units before the war to between 232 and 262 units by the time of the April ceasefire, and have since recovered to a level of between 234 and 278 units following partial replenishment [17]. This represents a decrease of at least 38% compared to pre-war levels [17]. DW reported that approximately 80% of THAAD stockpiles had been depleted in the course of responding to Iranian air defenses, with roughly half of Patriot stocks also consumed [11]. Peru's El Comercio reported that Patriot interceptor missile inventories had fallen by 65% compared to pre-war levels [9].

2. Current Situation

In early August, the US Department of Defense gave defense contractors a 21-day deadline to submit plans for accelerating production and delivery [13][9]. It was confirmed through a Washington Post memo that Deputy Secretary of Defense Steve Feinberg had sent a letter to defense industry leaders on Wednesday [13]. AP presented updated figures showing that THAAD stockpiles, which had fallen from 452 units before the war to 232–262 units in the early ceasefire period, had since recovered to a range of 234–278 units following partial replenishment [17].

India's Times of India, citing internal Department of Defense assessments, reported that approximately 80% of THAAD stockpiles and roughly 65% of Patriot stockpiles had been depleted, with ATACMS and PrSM approaching near-total exhaustion [15]. JoongAng Ilbo covered this under the headline "THAAD 80% Used," directly conveying warnings from senior US military commanders [1]. The article, citing CNN reporting, quoted a commander's statement that "the Department of Defense's munitions stockpiles are dangerously low" [1].

General Dan Caine, Chairman of the Joint Chiefs of Staff, was identified as the individual who directly briefed President Trump on the interceptor missile stockpile crisis. Austria's Die Presse reported that Caine, as "one of the decision-makers between the Pentagon and the White House," was understood to have informed Trump of the crisis situation [16]. DW raised the possibility that this stockpile shortage may have actually constrained the US military's strike options against Iran [11].

China's state-run Global Times treated this situation as an illustration of the material limits of American hegemony. The outlet commented on the depletion crisis with the phrase, "US strength once looked endless—until the day the warehouse says otherwise" [18]. This reflects Beijing's perspective on the constraints facing Washington's military projection capabilities.

3. Key Actors and Positions

US Department of Defense / Pentagon: Centered on Deputy Secretary Feinberg, the current top priority is pressuring defense contractors to accelerate production [13]. While there is a firm recognition of the urgency of restoring stockpiles, this effort runs up against the structural constraint that production capacity itself cannot be expanded in the short term.

US Joint Chiefs of Staff and Field Commanders: Military leadership, including Chairman Caine, is concerned that the munitions shortage adversely affects not only options against Iran but also readiness for contingencies in other regional conflicts [1][16]. Their concern lies less with the Iran war itself than with maintaining long-term readiness against China, Russia, and North Korea.

Iran: An analysis by Thomas Juneau of the Sana'a Center in Yemen assessed that the United States had failed to achieve any of its original objectives—regime change, dismantling the nuclear program, or reducing Iranian support for its proxies [6]. Given that Iran maintained its support for the Axis of Resistance through more than 100 days of fighting, Tehran tends to interpret this munitions depletion crisis as the result of its own strategy of endurance having exposed the physical limits of US capacity [14].

China: The tone of Global Times coverage focuses on framing America's munitions depletion as a structural limit on hegemonic capability [18]. This is a narrative that could influence Beijing's calculations regarding US intervention capacity in a Taiwan Strait or South China Sea contingency.

Defense Contractors: They have been required to submit plans for accelerated production and delivery within a 21-day deadline [13]. Whether THAAD and Patriot manufacturers, including Lockheed Martin, expand their production lines is the key variable that will determine the pace of future stockpile recovery.

4. Key Points of Contention

First, the degree of depletion of ground-launched precision strike weapons (ATACMS, PrSM) is more severe than that of air-defense interceptor missiles [4][15]. These weapons systems have long replenishment lead times, making short-term recovery difficult.

Second, reported figures for THAAD and Patriot stockpiles vary across news outlets. CSIS and AP put the THAAD reduction rate at above 38%, while DW cites an 80% depletion figure [17][11]. This discrepancy appears to stem from differing standards for "depletion" versus "usage relative to available stockpile," but it also attests to the fact that precisely grasping the actual state of affairs is itself sensitive security information.

Third, there is the question of whether the munitions stockpile shortage has actually constrained US military options against Iran [11]. This is a variable that will directly affect Washington's bargaining power in the coming phase of ceasefire negotiations.

Fourth, there is the question of the magnitude of the spillover effects of stockpile depletion on Indo-Pacific defense posture [1]. THAAD and Patriot are the same systems as those deployed in South Korea and Japan, while ATACMS and PrSM have been identified as core components of deterrence forces against China [4].

II. In-Depth Analysis of the Issue

The US Military Munitions Depletion Crisis in the Iran War: In-Depth Analysis

1. Analysis of Root Causes

The primary cause of this depletion crisis is the mismatch between operational design and actual demand. ATACMS and PrSM were originally deployed as strategic assets for anti-access/area denial in the context of China and Russia [4]. As these weapons were deployed to neutralize Iranian air defenses and strike targets, consumption occurred that was unrelated to their original purpose [4]. Depletion on the air-defense interceptor side is more structural in nature. THAAD and Patriot stockpiles fell sharply in the course of countering the low-cost, mass-scale missile and drone attacks conducted by Iran and the Houthis and other elements of the Axis of Resistance [11]. The asymmetry whereby the production cost and cycle for a single interceptor missile far exceed those of the attacking side's drones and missiles accelerated the pace of depletion.

The second cause is the duration of the war itself. The Trump administration declared at the outset of the war that it would pursue a "short, decisive intervention," but the conflict in fact dragged on for more than five months [14]. The Sana'a Center in Yemen pointed out that the United States failed to achieve any of its original objectives—regime change, blocking nuclear development, neutralizing missile and drone programs, and cutting off support for non-state armed groups—over the course of more than 100 days of fighting [6]. The failure to achieve these objectives led to an extension of operations, and this extended operational tempo in turn deepened the depletion, forming a self-reinforcing cycle.

The third cause is the limitations of peacetime stockpile policy. The US Department of Defense has not maintained stockpiles on the premise of simultaneous, large-scale attrition warfare on multiple fronts. The very fact that defense contractors were only required to submit accelerated production plans after receiving a 21-day deadline [13][9] shows that a rapid surge-production system had not been established in advance for contingencies.

2. Structural Context

In terms of security structure, this crisis has revealed a gap between the US military's principle of "multi-front readiness" and the actual availability of stockpiles. The fact that Chairman of the Joint Chiefs General Dan Caine directly briefed President Trump on the interceptor missile stockpile crisis [16] indicates that this issue was recognized at the highest levels not merely as one confined to the Iran front, but as a readiness problem for the armed forces as a whole. THAAD and Patriot are shared assets in the sense that they are also deployed for the defense of South Korea, Japan, and Gulf allies. This creates a structure in which depletion in one theater immediately erodes defensive capacity in another.

In terms of political structure, President Trump, having failed to even secure "an unstable ceasefire unlikely to be extended indefinitely" [10], finds himself in the position of having to defend, domestically, the legitimacy of continuing the war. CFR assessed that the options remaining to Trump—dramatic escalation, conciliatory de-escalation, or continuation of the current messy stalemate—are all unattractive [3]. The munitions shortage functions as a physical constraint limiting the feasibility of the escalation option among these.

In economic and industrial structure, the rigidity of the defense supply chain is central. Deputy Secretary of Defense Steve Feinberg's letter to the defense industry and the 21-day deadline requirement [13] attest to the fact that peacetime production lines cannot meet wartime demand. Precision-guided munitions have long supply chains involving semiconductors and specialty alloys, and rigorous verification processes, meaning that ramping up production takes anywhere from several months to several years. This is the same structural bottleneck that Western defense industries have repeatedly flagged since the war in Ukraine.

3. Comparison with Historical Precedents and Similar Cases

The closest precedent is the depletion of Western artillery shell, Javelin, and Stinger stockpiles in the early stages of the Russia-Ukraine war. At that time as well, peacetime stockpiles could not accommodate the demands of high-intensity attrition warfare, prompting discussions of increased production. The current crisis shows that those discussions recurred without ever having been carried through to implementation. The difference is that this time the problem has arisen with precision-guided munitions and interceptor systems—weapons systems with far higher unit costs and longer production lead times than those involved in the Ukraine war.

A contrast can also be drawn with Patriot operations during the Gulf War and Iraq War. At that time, Patriot use was confined to limited defense against Scud missiles, whereas in the current Iran war it has faced a multi-target situation requiring simultaneous defense of Israel, US military bases, and Gulf allies. This expansion of the scope of defense has structurally raised the rate of consumption compared to previous conflicts.

China's state media outlet Global Times characterized this crisis as a case revealing the material limits of American hegemony, commenting that "US strength once looked endless—until the day the warehouse says otherwise" [18]. This reflects a Chinese effort to interpret Western media coverage of stockpile depletion as a crack in the narrative of US military superiority. Iran's state media outlet Tehran Times likewise cited investigative reporting by Reuters, CBS, and CNN to characterize this as "an unprecedented wall of industrial projection capacity" [14]. Both outlets share the common feature of incorporating America's logistical limitations into their own strategic narratives.

4. Key Variables Shaping the Development of the Issue

The first variable is the direction of the Islamabad negotiations [12]. In the ceasefire negotiations between the United States and Iran, the right to uranium enrichment and the issue of disposing of Iran's 60%-enriched uranium remain the core points of contention [12]. If the negotiations succeed, further depletion will stop; if they collapse, air-defense stockpiles could be eroded further.

The second variable is the situation in the Strait of Hormuz. As long as Iran maintains its position of preserving control over the Strait as an asymmetric lever tied to regime survival [10], continued US naval operations in the Strait will keep generating demand for interceptor systems.

The third variable is the actual pace at which defense contractors ramp up production. Industry's response to the 21-day deadline requirement, and whether production lines are actually expanded [13][9], will determine the timing of stockpile recovery. The recovery of THAAD stockpiles to a level of 234–278 units following partial replenishment [17] is a signal that increased production is possible, but the fact that this remains at least 38% below the pre-war level of 452 units also simultaneously demonstrates the limits of the recovery pace.

The fourth variable is competition for stockpile allocation with other theaters, particularly deterrence postures against China and North Korea. Underlying senior Department of Defense commanders' warnings that the stockpile shortage is "dangerous" [1] is a concern that depletion on the Iran front could erode defensive capacity in the Indo-Pacific theater. How this allocation issue is resolved is a variable directly linked to the defense posture of allies such as South Korea and Japan.