The United States faces a strategic test as its missile defense stockpile strains under the pressure of a prolonged Iran conflict. Experts warn that extending the fighting could exhaust a stockpile that cannot be replenished at the pace of war.

Kelly Grieco, a senior fellow at the Stimson Center, warned, “You can’t replace those kinds of missiles overnight,” and added, “It would take years.”

The defense architecture relies on a mix of systems designed to destroy incoming missiles and drones, including the Patriot system, the Aegis Combat System, and THAAD, with launches from ships or land.

As of December 2025, the Missile Defense Agency’s arsenal numbers show the challenge: 414 SM-3 interceptors and 534 THAAD interceptors, while Patriot PAC-3 MSE production has risen to about 270 per year since 2015, CSIS reports.

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The systems most capable of stopping ballistic missiles are the SM-3s and THAADs, but they cost more and take longer to manufacture.

These numbers underscore the friction between rapid operation and the slower cadence of production.

During a recent period of high tempo activity, estimates suggest the U.S. deployed between 100 and 150 THAAD interceptors and 80 SM-3s in defense of allies, with Patriot interceptors defending key bases in the region.

More than 150 THAAD interceptors would amount to roughly 30 percent of the stockpile, a figure CSIS calls concerning.

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If the current Iran war runs longer, the stockpile could be depleted.

If the Iran war bled into multiple months and the U.S. interceptor usage rate was similar to that of the 12-day war, the U.S. could hypothetically deplete its entire interceptor stockpile, Grieco said.

Six U.S. service members died Sunday when their makeshift operations center at a civilian port in Kuwait was struck by a suicide drone.

The missed opportunity for air defense was the result of interceptor resources being stressed, Shapiro said, “If there was nothing deployed, that obviously contributed because what resources we had, had to be deployed elsewhere.” “If it was deployed, it was unsuccessful.”

Recognizing the need for more interceptors.

The Defense Department signed a contract with Lockheed Martin in January that will quadruple the yearly production of THAAD interceptors from 96 to 400 and boost the annual production of the PAC-3 MSE from 600 to 2,000.

But this isn’t something that will happen instantaneously. The PAC-3 agreement, for instance, is slated to take place over seven years.

At this time, the U.S. military cannot immediately increase the number of interceptors by a vast margin. “The Department of Defense is really good, but magic is still not one of its capabilities,” Grieco said.

The Trump administration is scrambling to replenish munitions resources and will host a meeting Friday with Lockheed Martin, RTX, L3Harris and other defense firm executives to discuss an uptick in missile systems production to replenish munitions used in the Iran war.

Stress on resources could also factor into the timeline for the conflict.

A dwindling amount of interceptors may have led to the end of the Twelve-Day War, according to Shapiro.

So many interceptors were used during that time that the U.S. and Israel were approaching interceptor inventory strain, he noted.

“My understanding was that had the conflict continued for another few days or another week or so, it could have become critical,” Shapiro said.

The volume of ballistic missiles Iran has fired from the first day of Operation Epic Fury has decreased by 90 percent, CENTCOM commander Adm. Brad Cooper said during a media briefing at MacDill Air Force Base Thursday.

Iranian drone attacks had also decreased by 83 percent since day one.

The drop in Iran’s rate of firing projectiles possibly means that the U.S. offensive against Iranian missile capabilities and missile storage facilities is working. At this time, however, that remains unclear.

Dr. Sanam Vakil, director of the Middle East and North Africa Program at Chatham House, said during an Atlantic Council roundtable that the calculus regarding Iran was unknown.

“Certainly on day six, it looks like its capability to launch missiles is maybe reduced, but it could also be deliberate,” Vakil said. “Iran is prepared for a longer war than I think the U.S. administration clearly calculated for.”

Iran could be conserving missiles to distract with multiple attacks in different domains and or to prepare for a military campaign that will come in waves, she said.

The question is whether Iran can continue its barrage of ballistic missiles and drones and outlast the interceptor stockpile the U.S. has.
The Pentagon continues to provide assurances that Iran is not capable of this feat.

“We’ve got no shortage of munitions,” Hegseth said at the media briefing at MacDill Air Force Base Thursday.

Cooper said U.S. combat power continues to escalate while Iran’s is in decline.

And Chairman of the Joint Chiefs of Staff Gen. Dan Caine, who spoke at a Pentagon briefing, addressed concerns regarding specific U.S. munitions shortages.

“We have sufficient precision munitions for the task at hand, both on the offense and defense,” Caine said. “But I want to tell you, teammates, as a matter of practice, I don’t want to be talking about quantities.”

Despite the confidence, Hegseth and Caine reportedly admitted during a briefing with lawmakers that Iran’s Shahed drones presented a problem for interceptors because they fly at a low altitude and can evade air defense systems.

Iran has no shortage of the unmanned aerial vehicles, reportedly producing 10,000 per month. The drones are also cheap to manufacture, costing between $20,000 and $50,000.

The unknown intended timeline for Operation Epic Fury also factors in. President Trump said this week that the military campaign could last four to five weeks, but that the U.S. had the capabilities to go far longer than that.

Hegseth, during a Pentagon briefing, implied the war could stretch up to two months, but reiterated the president’s point that the U.S. has enough munitions and equipment to beat Iran.

“The question is which clock will run first,” Soliman said.

Soliman noted that any boots on the ground, including Kurdish allies, has the potential to prolong the conflict, leading to potential U.S. interceptor depletion.

Shortly after this briefing, reports emerged that pro-American Iranian Kurdish forces were supplied with arms by the CIA and preparing to attack Iran.
The stress on the interceptor stockpile also depended on the endgame, Lipner said.
“It’s a race of attrition between the two sides to see who can get over the finish line before the other,” Lipner said.

Sen. Mark Kelly warned that if Iran has more offensive assets than the United States has defensive capacity, trouble could arrive quickly if our magazine depth runs to zero.

The United States launched Operation Epic Fury on Feb. 28, killing Iran’s supreme leader Ayatollah Ali Khamenei during the initial attack, leaving a vacuum of power that has yet to be filled.

Khamenei’s son is an early favorite to succeed him.

The Trump administration has laid out its objectives for the operation, including the decimation of Iran’s missile capabilities, navy and its nuclear facilities and program.

On Tuesday, Cooper announced that the U.S. had struck nearly 2,000 targets with more than 2,000 munitions.
In retaliation, Iran has launched over 500 ballistic missiles and over 2,000 drones.

Fifty thousand U.S. troops, 200 fighter jets, two aircraft carriers and bombers are currently stationed in the theater, with personnel and ordnance reinforcement on the way, Cooper said.

The U.S. has destroyed hundreds of Iran’s missiles, launchers and drones, focusing on shooting all the things that can shoot at us.
Cooper noted, during a briefing, that the United States has destroyed 30 Iranian navy vessels.

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