The scarcity of vital defensive ordnance, designed to safeguard US military personnel and their allies from Tehran’s projectiles, is set to influence any armed campaign against Iran, according to assessments from officials and experts.
Both the United States and Israel rapidly depleted their reserves of interceptors during the 12-day conflict last year, a period when Iran discharged hundreds of missiles towards Israel.
Now, the US armed forces are evaluating the probability that Iran’s reprisal will strain the availability of these crucial munitions, especially as efforts to replenish them face difficulties. This situation not only impacts the ongoing conflict in Ukraine but also Washington’s strategic blueprints for any potential confrontation with China or Russia.
The “magazine depth”—military terminology for the inventory of available ammunition—of the US’s Terminal High-Altitude Area Defense, or THAAD, anti-missile systems was a particular source of concern, noted a regional military representative.
They stated that the US deployed as many as 150 THAAD projectiles to defend Israel in the preceding year. Since the system became operational around 2010, fewer than 650 of these have been ordered in total.
Washington could “effortlessly” exhaust a “full year’s worth” of essential defensive munitions in just a single day or two of operations “if Iran were capable of launching multiple large volleys of missile and drone assaults” against US forces and Israel, explained Stacie Pettyjohn, who directs the defence programme at the Center for a New American Security think-tank.
The official indicated that there was little chance Iranian missiles would completely deplete the US military’s defensive armaments during combat. However, discussions have centered on the imperative to conserve these munitions for other operational zones, which might compel Israel to implement additional protective measures for itself while the US military shields its own troops and other partners, the official elaborated.
US, French, British, and other contingents assisted in shielding Israel from a barrage of hundreds of Iranian drones, cruise, and ballistic missiles in April 2024. These were fired in retribution for the assassination of Iranian officials. Nevertheless, no such multinational alliance has been formed for Israel’s protection this time.
Iran and its regional surrogate organizations have employed the “saturation” tactic: overwhelming an adversary’s sophisticated aerial defense systems by simultaneously launching massive salvos of relatively inexpensive missiles. This strategy has been incorporated into US planning for any offensive operation.
Both defensive and offensive “munitions would constitute a pivotal factor that the Pentagon would underscore as one of the potential repercussions of a conflict with Iran, particularly if the president were contemplating a more prolonged air campaign, rather than merely a few limited punitive strikes,” Pettyjohn observed.
During the conflict last year, the US navy also discharged at least 80 advanced seaborne missiles, including one designated the SM-3, which saw its inaugural combat deployment protecting Israel in April 2024, the official mentioned. Only 12 SM-3s, optimized for ballistic missiles, will be acquired this fiscal year for $445 million.
The Pentagon has stated its intention to allocate $840 million for 37 THAAD interceptors in the fiscal year 2026. Moreover, the US army requested $1.3 billion for 96 defensive Patriot missiles this current fiscal year.
Admiral James Kilby informed Congressional leaders in June of the preceding year that the navy had expended its interceptor missiles at an “alarming pace” during the 12-day hostilities.
By January 2025, the navy had also utilized approximately 200 SM-2 and SM-6 missiles during its operation against Houthi militants targeting maritime traffic in the Red Sea, according to a statement by Vice Admiral Brendan McLane, who heads naval surface forces, at a conference in the prior year.
That engagement also highlighted a challenge for the naval destroyers presently stationed near Iran: these vessels must return to port to restock their missile magazines, as they cannot be reloaded at sea.
Any “aerial campaign at this moment will be fundamentally governed by our ammunition inventory,” which has “been significantly taxed supporting various operations globally,” remarked Doug Birkey, executive director of the Mitchell Institute for Aerospace Studies think-tank.
Israel’s own inventory of interceptors is classified information, but their limited availability has been a concern for its military as Iran and the Tehran-backed Lebanese group Hezbollah have manufactured thousands of missiles over the last decade.
Throughout the 12-day conflict, Iran launched over 500 missiles at Israel. Roughly 35 managed to penetrate Israel’s multi-layered aerial defenses.
The military representative stated that the US and Israel had subsequently conducted “post-mortems” to ascertain if their constrained supply of defensive munitions had been deployed efficiently. They investigated the possibility that both armed forces had, in some instances, targeted the same incoming object.
Offensive ordnance would also present a limiting factor, analysts pointed out. In any confrontation, the US would be expected to fire Tomahawk missiles to avoid sending non-stealthy fighter jets into Iranian airspace.
The US utilized Tomahawks—which are launched from destroyers and submarines—in its campaign against Houthi rebels and last year’s aerial bombardment of Iran. Tomahawks would also be necessary in a conflict against Russia or China, Pettyjohn added.
The issue of munitions production has stemmed from inconsistent so-called demand signals, or long-term commitments to purchase them, from the Pentagon. Without multi-year contracts in hand, defense corporations were not incentivized to boost manufacturing. The US is now aiming to “supercharge” the production of some key munitions by forging agreements with major US manufacturers.
The regional official suggested it was not inconceivable that Iran’s reaction to strikes might be subdued, or akin to the orchestrated June 2025 assault on an American airbase in Qatar, after US President Donald Trump ordered air strikes on the Islamic republic’s three main nuclear facilities. However, that outcome was far from guaranteed, the official cautioned.
The “prudent application” of missiles is paramount when it comes to preserving ammunition inventory, Vice Admiral Charles Cooper told senators during his confirmation hearings to lead US Central Command, which encompasses the Middle East.
“We’ve progressed from launching $2 million missiles at $100,000 drones to just recently deploying $25,000 modified rockets from the Vietnam era against these drones,” he remarked.
Illustration by Ian Bott