Half of U.S. Missile Stocks Could Vanish in Just 7 Weeks of War

The Center for Strategic and International Studies’ latest analysis finds that during the first seven weeks of a war with Iran, the Pentagon would have used at least 45% of its Precision Strike Missile inventory, 50% of its THAAD interceptors, and nearly half of its Patriot ballistic-missile interceptors. The report cautions that while the U.S. still holds enough missiles to sustain that conflict, it could face shortfalls in a future Pacific theater confrontation. The study was authored by Mark Cancian, a former U.S. Marine Corps colonel, and CSIS researcher Chris Park.

CSIS estimates it would take between one and four years to rebuild seven key munitions stocks to prewar levels. The analysts warn the reduced inventories create near-term risks and note that a war with a capable peer such as China would burn through munitions far faster than the conflict with Iran has. They add that prewar stockpiles were already inadequate and that current levels would constrain U.S. operations in a future high-end fight.

◆ Trillion-dollar nation? Rising defense spending

In the past two months, the U.S. has moved quickly to replenish munitions, awarding multiple contracts to defense firms. The Pentagon says Honeywell Aerospace will expand production of key components for U.S. munitions stockpiles after a multi-year, $500 million investment. President Donald Trump has requested a $1.5 trillion defense budget for fiscal 2027, which the Defense Department calls the largest annual increase since World War II.

Using CSIS’s figures, Fortune estimates the U.S. has spent roughly $24 billion so far on seven major munitions. Analysts expect the full cost of a war with Iran would be far higher. Linda Bilmes, a public-policy expert and lecturer at the Harvard Kennedy School, told Fortune the administration is underestimating short-term expenses such as infrastructure damage and long-term obligations such as lifetime disability payments for thousands of veterans. She said the war could exceed $1 trillion in total costs.

The CSIS analysis stands in contrast to President Trump’s early public assessment of U.S. stockpiles. He said, “Stocks of medium- and heavy-grade munitions are larger and better than ever,” adding that “the U.S. essentially has unlimited quantities of these weapons.”

Pentagon chief spokesman Sean Parnell told Fortune the military has “everything it needs” to operate at the time and place the president selects. “Since President Trump’s inauguration, we have carried out multiple successful operations across combatant commands while maintaining deep weapons capabilities to protect the American people and U.S. interests,” he said.

◆ Growing concerns over munition spending

Experts such as Bilmes warn that the U.S. is spending vastly more per engagement than Iran does to produce its weapons. Reuters reports a single Iranian Shahed drone costs roughly $20,000–$50,000 to build, while a Patriot interceptor used to shoot down drones or more sophisticated aerial threats can cost about $4 million because of its complex technology. “The cost is not only high; it’s wildly disproportionate compared with drone production costs,” Bilmes said.

Demand for Patriot missiles is especially strong. Eighteen countries besides the U.S. operate the system, and the U.S. supplied about 600 interceptors to Ukraine and other allies during the conflict. Lockheed Martin plans to raise PAC-3 MSE production to 2,000 missiles per year by 2030, but CSIS analysts urge more careful allocation of existing stocks and annual deliveries. Current annual supply is roughly 600 missiles. Some strategists argue Patriots should be reserved for a potential conflict with China, while Ukraine and other allies continue to request additional munitions.

CSIS notes the Defense Department could substitute other air-to-air missiles, such as the AIM-120, but those cost roughly $1 million each. As cheaper interception options disappear, the U.S. and Gulf partners have resorted to gun-armed helicopters and fixed-wing aircraft as stopgaps. With resources constrained, some U.S. officials worry about how the country will sustain munitions procurement over the long term.

Arizona Democratic Sen. Mark Kelly told CNN last month that Iran “has the capacity to mass-produce Shahed drones, ballistic missiles, and medium- and short-range missiles, and it maintains large stockpiles. Eventually, this becomes a math problem. How do we resupply air-defense munitions? Where will the volume come from?”

/ Sasha Rogelberg & Taeyoung Kim young@fortunekorea.co.kr