US Faces Years-Long Wait to Replenish Iran War Weapons

The United States will need years — in some cases until late 2030 or early 2031 — to replenish stockpiles of advanced weapons systems heavily used in the 39-day air and missile campaign against Iran, according to a new analysis from the Center for Strategic and International Studies (CSIS) released Wednesday. The depletion has created what the think tank calls a “window of vulnerability” for a potential future conflict with China, raising serious concerns about military readiness and strategic deterrence.

The Scope of the Depletion

The analysis, authored by CSIS Senior Adviser Mark F. Cancian and Research Associate Chris H. Park, focuses on seven critical munitions systems. Three key systems — Tomahawk cruise missiles, THAAD interceptors, and Patriot interceptors — will require three or more years to return to prewar inventory levels.

According to AP News, the U.S. fired more than 1,000 Tomahawk cruise missiles at Iran during Operation Epic Fury. With prewar inventory estimated at roughly 3,100 and current production at approximately 200 per year, full replenishment is not expected until late 2030 to early 2031. The Navy has requested 785 Tomahawks in the FY 2027 budget — a dramatic increase from prior years.

For air defense systems, the picture is similarly stark. Between 190 and 290 THAAD interceptors were expended from a prewar inventory of roughly 360, with replenishment expected by mid-to-late 2029. The Army has requested 857 THAAD interceptors in FY 2027, and Lockheed Martin plans to quadruple production capacity from 96 to 400 per year. Patriot interceptors saw even heavier use, with 1,060 to 1,430 expended from approximately 2,330 prewar. Replenishment is projected for mid-2029, with the FY 2027 budget requesting 3,203 missiles.

The Problem: Time, Not Money

A central theme of the CSIS report is that the challenge is no longer primarily financial. “The problem today isn’t money; it’s time,” the report states. “It takes time to expand production capacity and to build these complex systems.”

President Donald Trump has proposed a historic $1.5 trillion defense budget for FY 2027 that significantly accelerates spending on high-end munitions — a ramp-up that began during the Biden administration. But even with bipartisan congressional support for boosting inventories, production capacity cannot be expanded overnight.

Mark Cancian, a retired Marine colonel, noted in an interview that the roots of the predicament trace back to the end of the Cold War, when the U.S. assumed future wars would be short and regional. “The thinking started to change, but it just takes time to build inventories,” Cancian said, adding that part of the challenge is bringing up to speed a complicated web of supply chains and subcontractors.

Cancian also credited the Biden administration for starting conversations with the defense industry and ramping up production. “A lot of people in the Trump administration are inclined to say that everything was terrible until they arrived, and that’s not true,” he said. “Now, it is true that the Trump administration really increased funding.”

Systems on Faster Timelines

Not all munitions face multi-year timelines. The Joint Air-to-Surface Standoff Missile (JASSM), of which more than 1,100 were expended from a prewar inventory of roughly 4,400, is expected to recover by mid-2027 due to existing high production rates of approximately 500 per year. The Precision Strike Missile (PrSM), a newer system with a small prewar inventory of roughly 90, saw only 40 to 70 expended and should return to prewar levels by late 2026.

Standard Missiles (SM-3 and SM-6), used less heavily by naval assets positioned farther from the conflict, are expected to return to prewar levels by early 2029 and late 2028 to early 2029, respectively.

Strategic Implications and China Deterrence

The depletion has created what CSIS calls a “window of vulnerability” for a potential Western Pacific conflict, particularly with China over Taiwan. China has a stated goal of being capable of taking Taiwan by force by 2027, though experts view this as more aspirational than a hard deadline.

The CSIS report, however, notes that the situation is “not all bleak.” The U.S. military has recently demonstrated its capabilities against Iran, Venezuela, and the Houthi rebels in Yemen. “China is deeply aware that it has no recent combat experience and that it performed poorly in its last war — against Vietnam in 1979,” the report said. “That difference in experience may preserve deterrence until munitions inventories are restored.”

Political and Congressional Dynamics

The munitions depletion has become a flashpoint in Washington. Defense Secretary Pete Hegseth faced bipartisan criticism during congressional hearings on May 12, with Sen. Chris Coons (D-DE) warning that the administration had achieved “a series of tactical successes but are on the verge of a strategic loss.” Hegseth pushed back, telling lawmakers, “I take issue with the characterization that munitions are depleted in a public forum. That’s not true.”

For Democrats, the depleted stockpiles serve as a metric against the Iran war, which Trump launched without congressional approval. Some Republicans, meanwhile, blame Patriot shipments to Ukraine for the depletion. The war has cost approximately $29 billion, with roughly $24 billion related to replacing munitions and repairing equipment, according to Pentagon officials.

Allied Competition for Limited Production

Complicating the replenishment effort is the fact that U.S. allies have placed large orders for the same systems, creating competition for limited production output. Japan has ordered 400 Tomahawks, Saudi Arabia 730 Patriot interceptors and 360 THAAD interceptors, Germany 600 Patriot interceptors, and Ukraine has received more than 600 Patriot interceptors. Poland has ordered 821 JASSMs, and Australia more than 200 Tomahawks.

“Patriot deliveries pose a dilemma for the United States because of the need to replenish its own inventories, help Ukraine defend against Russian missile attacks, and meet the needs of 17 other countries that use the interceptor,” the CSIS report noted.

What to Watch For

The coming months will be critical as Congress considers the $1.5 trillion defense budget and an expected war supplemental. Key questions include whether industry can meet ambitious production targets, how the administration will balance U.S. replenishment needs with allied demands, and whether the ceasefire with Iran holds. If renewed hostilities break out, stockpiles could be further depleted, extending the timeline for recovery and deepening the window of vulnerability.