How Iran is Depleting US Weapons Stocks
The war against Iran is beginning to reveal deeper issues for the United States military. It is not merely a question of how many Iranian missiles are successfully intercepted, but how many expensive interceptors the US must fire to stop them, and how quickly the American defence industry can replace the weapons used.
The latest picture emerged during Iran’s attack on the Muwaffactory Salti Air Base in Jordan. The US military fired up to approximately 70 Patriot interceptors and more than a dozen THAAD interceptors when facing a barrage of Iranian missiles. This level of usage is equivalent to about one week of usage at previous levels in the war, as reported by The Wall Street Journal on Wednesday, 16 September 2026.
The attack highlights the mathematical problem increasingly facing the American air defence system. Iran does not need to destroy entire US defence batteries to exert pressure on its military capabilities. Repeated attacks that force Washington to continuously fire high-value interceptors can deplete supplies faster than the defence industry can produce replacements.
The Wall Street Journal also reported that Iran has been using increasingly sophisticated attack tactics, including warheads that can split into multiple projectiles when approaching a target. This change makes the interception process more difficult and can increase the amount of ammunition required by the defending party.
Half to Two-Thirds of Interceptors Depleted
These developments coincide with an increasingly clear picture of depleting American weapons supplies. In an analysis released on Tuesday, 15 September 2026, the Congressional Budget Office (CBO) estimated that the conflict has exhausted approximately half to two-thirds of the combined supplies of several types of US missile defence interceptors since June 2025.
The weaponry included in this calculation comprises Patriot, Terminal High Altitude Area Defense (THAAD), Standard Missile-3 (SM-3), and Standard Missile-6 (SM-6). The Pentagon has not disclosed the exact number of interceptors in its inventory. Therefore, the CBO made estimates by comparing reported usage numbers with the total number of missiles known to have been purchased by the US Department of Defense.
The CBO estimates that these four types of interceptors account for $13.1 billion of the approximately $21.7 billion in ammunition that needs to be replaced after use up to 1 August. Land-attack cruise missiles account for about $7.3 billion, while other ammunition accounts for approximately $1.2 billion, as reported by Defense News on Tuesday, 15 September 2026.
The scale of this consumption demonstrates that defence costs do not stop once an Iranian missile is successfully destroyed. Every interceptor fired simultaneously reduces the reserves that may be required to face the next attack.