The U.S. Is Low On Munitions. How Can It Replenish Its Stockpiles?

As the U.S. war with Iran enters its seventh month, Reuters has reported that the U.S. Army has “used up much of its global stockpile of highly accurate long-range missiles.” Throughout the war, the United States has used weapons such as Army Tactical Missile Systems and Precision Strike Missiles to attack targets in Iran and the anti-ballistic missile systems Patriot and THAAD to defend against Iranian attacks. Due to the constant use of these weapons throughout the war, Reuters reported that U.S. stockpiles of defensive weapons “were dwindling.”

The Center for Strategic and International Studies further contributed to these findings. In a report published on July 27, CSIS tracked inventory figures for Patriot missiles and THAAD interceptors throughout the war. In its assessment of the situation, CSIS wrote that the U.S. had 2,330 Patriot missiles and 452 THAAD interceptors on February 27. But by July 27, CSIS estimated that the U.S. inventory of Patriots had declined from 2,330 on February 27 to between 759 and 827. Similarly, CSIS estimated that THAAD interceptors declined from 452 on February 27 to between 234 and 278 on July 27.

U.S. President Donald Trump has dismissed reports of the drawdowns of U.S. stockpiles, arguing that the “U.S. has massive amounts of ‘munitions,’ especially of certain types.” He added that “large amounts are being manufactured and shipped to the U.S. as needed.”

Similarly, U.S. Secretary of Defense Pete Hegseth has rejected claims that U.S. stockpiles have diminished. When asked about whether the U.S. is facing a munitions stockpile crisis, Hegseth stated that it was a “manufactured story.” He added that America’s “stockpiles are great, and they’re only getting stronger.”

The discussion about U.S. munitions and stockpiles has forced defense companies, policymakers, and defense experts to re-evaluate how American weapons are produced. Following the end of the Cold War, munitions procurement in the United States began to shrink. Some manufacturers shut down, as large-scale defense production was no longer necessary. Keeping production lines open was also expensive. Additionally, a report published by the U.S. Department of Defense found that the “number of companies within the defense industrial base shrunk dramatically,” as the defense sector transitioned from “51 to 5 aerospace and defense prime contractors.”

“When the Cold War ended, the United States changed its expectation from a great power war to short regional wars against opponents like Iraq or North Korea. That did not require a large munition inventory. As a result, inventories shrank,” Mark Cancian, a Senior Adviser with the Defense and Security Department at the Center for Strategic and International Studies, told me in an interview.

But when Russia launched its full-scale invasion of Ukraine on February 24, 2022, and when the U.S. war with Iran began on February 28, 2026, this led to an increased demand for Western weaponry. The need for and use of these weapons have vastly outpaced supply and production. As a result, this has strained the defense industrial base.

“The fundamental challenge with the current munitions, such as Tomahawks and Patriots, is that they are really good systems, and they are proven. They were designed a long time ago, and they were designed principally for performance. They were not designed for producibility, to be produced in scale,” Dr. Jerry McGinn, the Director of the Center for the Industrial Base at the Center for Strategic and International Studies, told me in an interview.

It takes time to produce these sophisticated weapons. According to a report published by The Hill, it will take “at least a few years” for the U.S. to replenish its stockpile to the pre-Iran war levels. Why is this the case?

“If you want more capacity, you have to build it,” McGinn explained during our discussion. “Building takes a while. You need permits and approvals, then you need to build it and have it qualified. In that case, it is hard to speed up how they are produced.”

Cancian noted that today’s deliveries were funded in 2023 and 2024. For the U.S. THAAD inventory, CSIS found that previous budget documents had projected zero deliveries between August 2023 and April 2027. The CSIS report added that deliveries appeared to have been re-sequenced, likely diverted from allies, given the increased demand and need for these systems. The Trump Administration’s fiscal year 2027 budget, if approved, has $11 billion for THAAD, but deliveries will not begin until mid-2029. The CSIS report adds that deliveries will “complete the replacement of Iran War usage” by the “end of calendar year 2029.”

CSIS found the same for Patriot deliveries. The FY 2027 procurement will start delivery in May 2029, and Cancian informed me that Patriot prewar inventory levels will not be reached until 2030. In other words, it will take over three years before new deliveries rebuild inventories to prewar levels. Meanwhile, Russia’s full-scale invasion of Ukraine and the U.S. war with Iran are still ongoing and may demand more missiles.

“The greatest problem is with shortages of anti-missile defenses, Patriot and THAAD, because there are no good substitutes,” Cancian told me. He also noted that there has been a shift in what has been constraining U.S. defense production.

“For a long time, the constraint was funding because munitions had lower priority and competed poorly in the Pentagon’s budget process,” Cancian explained. “The Biden Administration began increasing funding, and the Trump Administration accelerated that. Now, the constraint is capacity. That is increasing, but it takes time to hire new workers, build new factories, and purchase machinery.”

But there are a few ways to address these time constraints. For example, the U.S. has announced plans to build new factories to boost production. The U.S. Army broke ground on a demilitarization facility in Oklahoma in March, and it broke ground on an ammunition production facility in Iowa in July. Similarly, the U.S. Army opened a new artillery plant in Kansas in April. While it will take time for these facilities to produce new defense equipment and weapons, their creation will allow the United States to build greater capacity.

The Trump Administration has also called on its NATO allies for greater burden sharing, a term that refers to the fair distribution of costs, tasks, and responsibilities. Following the conclusion of the 2026 NATO Summit in July, the White House published a fact sheet stating that the Alliance has moved “toward greater burden sharing and self-reliance.” Should these discussions materialize, co-production of weapons, especially overseas, could help with capacity. While this will ease the demand on the U.S. to produce new and current weapons, it will also take time to achieve these goals.

Overall, Russia’s full-scale invasion of Ukraine and the U.S. war with Iran have forced a conversation among defense companies, policymakers, and defense experts about the defense industrial base. In its current state, it was not designed to sustain this level of demand for weaponry. It also appears that the time required to build these weapons is the most pressing issue. Industry leaders will continue to study ways to reduce production times without sacrificing the quality or reliability of these sophisticated weapon systems.

Disclaimer: Mark Temnycky was a defense contractor who provided contract support to various divisions within the U.S. Department of Defense’s Office of the Under Secretary of Defense for Acquisition and Sustainment from June 2018 to March 2025. In this capacity, he wrote congressional reports, conducted legislative audits, and prepared briefings and action memos for senior government officials on topics pertaining to defense acquisition and defense innovation. As a defense contractor, his contract support work did not address or cover munitions stockpiles, defense production, defense manufacturing, or weapons contracting. As of March 2025, he is no longer a defense contractor.