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August 3, 2026 • 9:00 – 10:00 am EDT
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Six Reasons Why the United States Is Low on Munitions
Photo: U.S. Army photo by Capt. Frank Spatt/DVIDS
The United States’ shortage of key munitions has entered the national debate and reportedly become a major element in presidential decisionmaking in the ongoing U.S. conflict with Iran. Use during the war against Iran is indeed a major driver of the issue, but it is not the only one. There are other reasons—strategic, industrial, institutional, and operational—why the Department of Defense (DOD) lacks the depth of munitions inventories that it needs today. Understanding the full history is necessary to fix the problem.
1. The war against Iran is an important driver.
This is obvious but bears reviewing. CSIS has documented the effects of the war on seven munitions used extensively in the war against Iran and that would also be used in a conflict in the western Pacific against China. These fall into two groups: missile defense and long-range ground attack.
The United States has used about half of the initial inventory for three of these munitions (Patriot, THAAD, and PrSM) and about one-third of the initial inventory for the rest (JASSM, SM-2/3/6, and Tomahawk). Even so, enough remains for any plausible scenario in the war against Iran. The risk comes from potential future wars, particularly with China—but potentially also with Russia or North Korea. Even before the current war, many analyses showed a need for larger munition inventories. Operation Epic Fury has exacerbated this munitions problem, and a multiyear rebuild now looms ahead.
Not all munitions are in short supply because of the war. As CSIS has described, the United States has deep inventories of cheaper alternatives, but these come with trade-offs. JDAM, for example, has the same precision and explosive yield as Tomahawk or JASSM. However, it is short-ranged and requires aircraft to overfly adversary territory, resulting in greater vulnerability and potentially greater losses.
Other munitions are in short supply, but not because of the war with Iran. Long-range anti-ship munitions, such as LRASM, Maritime Strike Tomahawk, and the Naval Strike Missile, would be critical in a war against China. They have not been used at all or only in small numbers against Iran. While their inventories have been largely unaffected by this war, existing inventories would rapidly dwindle in a war against a near-peer naval power.
2. The post–Cold War strategy required fewer munitions.
During the Cold War, the United States faced a superpower competitor in the Soviet Union, so a potential conflict required a large munitions inventory. When the Cold War ended, the strategy and requirements changed. Instead of a great power war, the United States would prepare for two limited regional conflicts. The notional adversaries were Iraq and North Korea. These wars were expected to be relatively short and therefore required far fewer munitions than a war against the Soviet Union. Munitions procurement shrank substantially. Expectations began changing in 2014 when Russia invaded Crimea and the Donbas, and as China continued its aggressive actions in the South China Sea. However, it was not until Russia invaded Ukraine in 2022 that the need for larger munitions inventories became clear and pressing.
3. The industrial base was designed for efficient peacetime production, not surge.
When the Cold War ended, the DOD realized that the smaller budgets of the post–Cold War world would not support the large existing defense industrial base. In 1993, then-Deputy Secretary of Defense William Perry gathered defense industry executives for what became known as “the Last Supper.” He told them to merge or diversify. They did. The result was a much smaller defense industrial base. The number of aerospace and defense prime contractors, for example, decreased from 51 to 5; the number of subprimes decreased commensurately. The whole structure got smaller.
The defense industry not only got smaller but, driven by the change in strategy, restructured itself for efficient production at peacetime rates. Surge capability was regarded as unnecessary and wasteful. As a result, very little spare capacity was available when the DOD decided to surge some production in 2022.
4. Munitions compete poorly in the Pentagon’s budget process.
Regardless of the defense budget’s size, the military services must always make trade-offs. In procurement, they face a trade-off between buying munitions or platforms such as aircraft, armored vehicles, and ships. Platforms have the advantage of operating for 30 years, being highly visible, and therefore contributing to deterrence. Munitions go into a bunker after production and only come out if there is a war or their service life has expired. Thus, munitions have often served as bill payers for higher-priority needs despite recognition of their importance.
5. The use of munitions in recent wars has reduced inventories.
Wars fought by the United States in the past half decade have required high-end munitions at levels not needed during the counterterrorism campaigns of the early twenty-first century.
Both the Biden and second Trump administrations expended munitions in the Middle East to deal with the regional war precipitated by Hamas’s October 7 attack on Israel.
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Under President Biden, the campaign against the Houthis—Operation Poseidon Archer—used hundreds of SM-2/3/6 ship-based interceptors. Expenditure of these expensive interceptors declined as the Navy became more proficient at shooting down Houthi drones and missiles with less expensive air-to-air and ship-based alternatives.
More sea- and ground-based interceptors were used in response to Iranian strikes against Israel in the April and October 2024 exchanges of fire between Iran and Israel. In the second Trump administration, U.S. forces reportedly fired 150 THAAD interceptors during the Twelve Day War.
In addition to missile defense munitions, the Middle East wars also used many long-range strike munitions. The Biden administration’s campaign against the Houthis used at least 135 Tomahawk missiles; 24 were fired during the Twelve Day War under Trump. These high-end strike munitions were used in other campaigns, too, including 16 Tomahawks launched against ISIS sites in Nigeria on Christmas Day 2025 and several dozen JASSMs used in the Venezuela raid of January 2026.
6. Transfers to Ukraine are a minor factor—with one important exception.
Administration officials have pointed to the transfer of weapons to Ukraine as an explanation for depletion of the U.S. munitions arsenal. The United States has indeed provided Ukraine with a lot of military equipment, including weapons, munitions, and supplies. The DOD’s fact sheet on Ukraine lists 102 items at a total cost of $85 billion.
However, the vast majority of items provided to Ukraine relate to ground combat. Some examples include light, medium, and heavy trucks; armored vehicles such as Abrams tanks and Bradley fighting vehicles; M113 armored personnel carriers; artillery ammunition; artillery howitzers; anti-tank weapons such as Javelin and TOW; mortars and related ammunition; and rifles and related ammunition. These systems have not played a major role in the war against Iran, and their inventories would be only a minor factor in a war against China. Transfers did include many experimental counter-drone systems, but these were essentially prototypes and not programs of record requiring wartime inventories.
Only four of the 102 listed items the United States have supplied to Ukraine have been used in the air war against Iran:
- About 600 Patriot interceptors have been sent to Ukraine since the beginning of the war. These missiles have protected Ukraine against Russian ballistic missile attacks. Some Patriots were drawn from U.S. inventories. Others were newly manufactured under the Ukraine Security Assistance Initiative (USAI) or supplied by Europe and so did not reduce U.S. inventories. Ukraine reportedly has few remaining, and President Zelensky is reportedly seeking 300 by this winter.
- The Biden administration supplied Ukraine with “several hundred” ATACMS in November 2024 after a lengthy debate, although Ukrainian reporting puts the number at 50. The United States is procuring the successor system to the ATACM, PrSM.
- High-speed Anti-Radiation Missiles (HARM) have been supplied to Ukraine since the summer of 2022. While the exact number sent is uncertain, the United States has a large inventory from decades of procurement. More than a thousand updated variants of the missile, AARGM and AARGM-ER, were estimated to be in U.S. inventory before the Iran war.
- Most of the U.S. Stinger inventory went to Ukraine. A few appear to have been sent to the Middle East for counter-drone operations. The remaining inventory is small. However, several new short-range air defense systems are coming online, such as the Maneuver Short-Range Air Defense System (Army) and the Marine Air Defense Integrated System (Marine Corps).
These munitions would be needed in a war against China. Table 1 shows these systems and the effect of transfers to Ukraine on inventories. The Trump administration has considered sending strike munitions with even longer ranges to Ukraine—Tomahawk and JASSM-ER (500–1,000 miles in range vs. 180 miles for ATACM)—but has not done so yet.
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What Does This Mean?
Using munitions is not necessarily a bad thing. They exist to be used. The question facing the United States is whether the risk in a future conflict arising from reduced inventories is worth the gain in the current conflict. That is a political question about which the country is deeply divided.
The United States is surging production of key munitions as fast as it can. The process began during the Biden administration, accelerated with the Trump administration’s reconciliation bill, and will accelerate again if the proposed FY 2027 budget is enacted.
A major lesson from this history is that commitment must be sustained. A few years of frenzied buying will not fully build inventories and will not establish the surge capacity that might be needed in a future conflict. The history also shows that aid to allies and partners is, in general, not a problem but is an issue for a handful of scarce munitions.
The immediate problem is not money, but time. Current deliveries reflect funding before FY 2024, as it takes two to four years for munitions to be delivered once a contract is signed. With time, production will equal demand, but that is several years in the future. Until then, there is a window of vulnerability.
Mark F. Cancian (Colonel, U.S. Marine Corps Reserve, ret.) is a senior adviser with the Defense and Security Department at the Center for Strategic and International Studies (CSIS) in Washington, D.C. Chris H. Park is a research associate for the Arleigh A. Burke Chair in Strategy at CSIS.