US Missile Stockpile Depletion Stemming from the Iran War and South Korea's Defense Posture Response

Executive Summary

As the Iran War, which began in February 2026, has turned into a protracted war of attrition lasting more than five months, US interceptor missile stockpiles have declined by at least 38 percent for THAAD and by as much as 65 percent for Patriot. Replenishment is expected to take several years due to bottlenecks in component production, and the resulting depletion is spilling over into the broader US deterrence posture toward China and North Korea, compounded by the absence of aircraft carrier presence in the Western Pacific and a 25 percent loss of MQ-9 drones. This is judged to be less a temporary shock triggered by the Iran War than the surfacing of a chronic underproduction structure in the US defense industry. Rather than demanding detailed inventory figures for US Forces Korea assets, South Korea needs to concentrate its negotiating leverage on discussions over allocation priorities in contingencies, while shifting budgetary and policy priorities toward the early fielding of indigenous interceptor systems such as L-SAM.

I. Issue Situation Analysis

Issue Situation Analysis: US Ammunition Depletion Stemming from the Iran War and Allied Defense Posture

1. Background and Development of the Issue

○ On February 28, 2026, the United States and Israel launched airstrikes against Iran - Operations codenamed "Monumental Fury" and "Roaring Lion"[8][5] - Israeli airstrikes resulted in the death of Supreme Leader Khamenei[6] - This did not lead to regime collapse, and Iran retaliated immediately[6]

○ Gap between the Trump administration's initial design and the actual course of the war - Initially set the goal of "short, decisive intervention"[2][8] - As of August, the war has turned into a protracted attrition conflict lasting more than five months[2][6] - Tehran Times assessed this as an "unprecedented wall of industrial projection capacity"[2]

○ Confirmation of the intensity of air defense operations across the Gulf - The UAE announced it had intercepted 537 ballistic missiles since February[1] - An additional 2,256 drones and 26 cruise missiles were intercepted[1] - Patriot and THAAD batteries across the Gulf region engaged simultaneously[1]

○ Concurrent depletion of precision-guided munitions - Ground-launched ATACMS and PrSM missiles have been virtually exhausted[2][9] - Approximately half of Tomahawk cruise missile stocks have also been consumed[9] - These assets were originally strategic reserves intended for contingencies involving China, Russia, and North Korea[2]

2. Current Situation

○ Extent of interceptor missile stockpile decline (figures vary by institution) - The Atlantic Council estimates depletion of up to three-fifths of Patriot stocks and up to half of THAAD stocks[3] - According to CSIS tabulations, THAAD stocks fell from 452 units to between 232 and 262 units[2] - Australia's CSIS presented a decline in THAAD stocks from 452 units to approximately 250 units, and in Patriot stocks from 2,330 units to approximately 800 units[15] - EAI's tabulation indicates a decline of at least 38 percent in THAAD stocks and 65 percent in Patriot stocks relative to pre-war levels[2]

○ Structural bottlenecks in replenishment - Experts project that full replenishment will take several years[3] - The manufacturing of a specific component in the Patriot production process constitutes the largest bottleneck[19] - Short-term production increases are not possible with current manufacturing capacity[19]

○ Effects on internal White House deliberations - The stockpile decline is factoring into discussions over the timing and conditions of negotiations with Iran[3] - Indian media pointed to the possibility of weakened deterrence vis-à-vis Russia and China[11] - US Central Command suggested the possibility of resupply from globally deployed stocks[11]

○ Naval assets also remain tied down in the Middle East for an extended period - The Pacific-based aircraft carrier USS George Washington was redeployed to the Middle East[13] - The USS Abraham Lincoln, originally scheduled to return in May, has had its deployment extended[13][17] - Increased Chinese activity has been observed amid the resulting absence of carrier presence in the Western Pacific[13]

○ Drone capabilities have also been depleted concurrently - The loss of 45 MQ-9 Reaper drones represents 25 percent of Air Force Reaper inventory[5][12] - A substantial share of these losses resulted not from being shot down but from crashes caused by lost communication links[5][12] - Marine Corps-operated Reapers have sustained no losses, suggesting that Indo-Pacific assets are managed separately[5]

3. Key Actors and Positions

○ The Trump administration - Considering reflecting stockpile depletion in the terms of negotiations to end the war with Iran[3] - Shifted toward a low-key approach, with an inclination to refrain from further large-scale strikes[11] - Adopting a cautious posture out of concern that escalation would further strain stockpiles[11]

○ The Iranian government and the Islamic Revolutionary Guard Corps - Aware of indications that Patriot, THAAD, SM-3, and SM-6 stocks held by US forces in the Gulf are running low[14] - High-intensity operations around the Strait of Hormuz have caused US Reaper losses[5] - Rebutting US claims of "control" in an attempt to avoid appearing at a negotiating disadvantage[16]

○ Gulf allies (including the UAE) - Disclosed large-scale interception results achieved by their own air defense networks, underscoring the severity of the threat[1] - Closely attentive to the effect of US asset depletion on remaining regional defense capacity[1]

○ South Korea - Raised the need to establish a channel for confirming the status of available THAAD assets[2][5] - Discussed early fielding of indigenous interceptor systems such as L-SAM[2][5] - Expressed concern over the continuity of strategic asset deployments by US Forces Korea[2]

○ Japan - Raised the need to expand joint production of PAC-3[2] - Examining responses to the possibility of weakened credibility in US extended deterrence[2]

○ The Philippines - Raised the need to establish contingency plans under the Enhanced Defense Cooperation Agreement (EDCA)[2]

○ Australia - A bipartisan think tank (CSIS) urged large-scale investment in top-tier missile interceptor systems[15] - Facing pressure to expand its own procurement, citing figures on the decline in US stockpiles[15]

○ US media and expert groups (Brookings, Atlantic Council, etc.) - Warned of declining credibility in extended deterrence and possible weakening of deterrence against China and Russia[3][11] - Cited the Russia-Ukraine war as a precedent for US stockpile depletion[14]

4. Key Issues

○ Uncertainty over stockpile figures - Estimates of the decline vary by institution (Patriot 60–65 percent, THAAD 38–50 percent)[2][3][15] - In the absence of official Department of Defense disclosures, figures rely on media and think tank estimates[3][15]

○ Replenishment timeline and the extended deterrence gap - The prevailing view is that recovery will take several years due to production bottlenecks[3][19] - The key issue is whether simultaneous crises, such as those in the Taiwan Strait and on the Korean Peninsula, can be managed during this gap period[2][5]

○ Priority conflicts over asset redeployment - Whether pressure on Indo-Pacific force allocation stemming from Middle East attrition will persist[5][13] - Internal priority adjustments suggested by differing asset management practices between the Marine Corps and the Air Force[5]

○ Intensifying pressure on allies for their own procurement and force buildup - Australia, South Korea, Japan, and others are simultaneously discussing reducing dependence on the United States[2][15] - Whether expanded joint production and indigenous development will provide a viable alternative remains uncertain[2][15]

II. In-Depth Issue Analysis

In-Depth Issue Analysis: US Ammunition Depletion Stemming from the Iran War and Allied Defense Posture

1. Root Cause Analysis

○ Concentrated depletion in a single theater of assets intended for multiple fronts - THAAD and Patriot were originally strategic assets intended to deter China, Russia, and North Korea[2] - These assets were committed to the unplanned theater of the Iran War[2] - "The impact of the stockpile depletion is significant precisely because these weapons were not originally designed for operations against Iran, but were strategic assets held in reserve for other fronts such as China, Russia, and North Korea"[2]

○ Iran's saturation attack tactics and the imbalance in interceptor consumption rates - The UAE alone intercepted 537 ballistic missiles and 2,256 drones[1] - Interceptor systems typically expend one to two interceptor rounds per incoming projectile - The asymmetry between the attacker's low-cost mass production and the defender's high-cost precision production has deepened

○ Structural bottlenecks in the production process - A specific component in the Patriot manufacturing process constitutes the greatest bottleneck point[19] - Production of this bottleneck component cannot be increased in the short term with current manufacturing capacity[19] - Experts project that full replenishment will take several years[3]

○ Strategic miscalculation by the Trump administration - Initially envisioned as "short, decisive intervention," but instead became a war of attrition lasting more than five months[2][8] - Tehran Times assessed that the operation had "run into an unprecedented wall of industrial projection capacity"[2] - Despite the decapitation operation (resulting in Khamenei's death), the Iranian regime survived and retaliated immediately[6]

2. Structural Context

○ Chronic underproduction structure in the US defense industry's manufacturing capacity - The Iran War has compounded stockpile pressures that had already accumulated since the Ukraine war - A Czech outlet assessed that "the United States has depleted its ammunition stocks to the point where it must now think about war differently"[19] - Support for Ukraine and consumption from the Iran War are competing for the same production lines

○ Zero-sum deployment of naval forces across theaters - The Western Pacific-based carrier USS George Washington was redeployed to the Middle East[13] - Increased Chinese activity has been observed amid the resulting absence of carrier presence in the Western Pacific[13] - The USS Abraham Lincoln has had its deployment extended, exposing crew mental health and resupply problems[13][17]

○ Bifurcated management of drone forces by theater - Losses have been concentrated in the 45 Air Force-operated MQ-9 Reaper drones (25 percent)[5][12] - Marine Corps-operated Reapers have sustained no losses, suggesting that Indo-Pacific assets are managed separately[5] - Airframes optimized for low-intensity conflict have exposed structural vulnerabilities against Iran's high-intensity integrated air defense network[5]

○ A dual bottleneck arising from dependence on Chinese supply chains - A substantial share of the key materials and components required for precision-guided munitions production depends on Chinese supply chains - This creates the paradoxical structure in which the replenishment of weapons meant to deter China is itself constrained by China-dependent supply chains[9]

○ The credibility of extended deterrence has become a political function - Rather than stockpile depletion itself, allies' "confidence in availability" is the substantive variable determining deterrence - Former National Assembly member Kim Jong-dae diagnosed that "this is not simply a contingent variable produced by the US-Israel-Iran war. It is a structural crisis that had already been foretold long ago, and a sign of the 'strategic menopause' befalling the great hegemon that has dominated the world since the end of the Cold War"[7]

3. Historical Precedents and Comparative Cases

○ Structural similarities with the Ukraine war artillery shell shortage - A precedent in which insufficient 155mm artillery shell production capacity repeatedly delayed Western support - A Czech expert assessed that similar bottlenecks mean that "no good solution is in sight" for further support to Ukraine[19] - In both cases, delays in expanding production lines for conventional munitions and precision-guided weapons constitute the key constraint

○ Contrast with the 2003–2011 dual-front operations in Iraq and Afghanistan - At that time, too, conducting two simultaneous fronts in the Middle East created pressure on asset allocation - However, the current situation is distinct in that it is concentrated on high-value precision weapons, namely air defense interceptor systems - The Iraq and Afghanistan wars centered on ground force attrition, whereas the Iran War centers on missile defense system attrition

○ A break from Patriot operational experience in the Gulf War (1991) and the early stages of the Iraq War - In the earlier Gulf War, Patriot use was relatively limited to intercepting low-intensity Scud missiles - The current Iran War involves countering combined saturation attacks of ballistic missiles, drones, and cruise missiles - The rate of interceptor consumption is estimated to be markedly steeper than in the past

4. Key Variables Shaping Future Developments

○ Timing and terms of a ceasefire negotiation - The stockpile decline is a substantive factor in White House discussions over the timing and terms of negotiations with Iran[3] - Indian media forecast that the stockpile decline would also affect whether further strikes on Iran occur in the future[11] - US Central Command has suggested the possibility of resupply from globally deployed stocks, though the scale remains unclear[11]

○ Pace of production increases and political budget allocation - Whether Congress allocates emergency funding for increased production - Whether diversification of the bottleneck component's supply chain succeeds will determine the timing of replenishment

○ The possibility of simultaneous pressure from Iran, Russia, and China - There is a risk that the stockpile gap period could induce opportunistic behavior - The key question is in which theater—the Taiwan Strait, the Korean Peninsula, or Eastern Europe—a test will emerge

○ Allied movements toward expanded indigenous procurement and production - Australia faces pressure to expand its own interceptor system budget following recommendations from CSIS[15] - Whether South Korea and Japan accelerate discussions on reducing dependence on the United States, including through expanded PAC-3 joint production