In the current conflict the short-answer from open reporting is this: the interceptor stocks on the US and Israeli side are closer to running out first than Iran’s ability to keep launching missiles at scale. Interceptor inventories were already drawn down by intense exchanges last year and in the opening days of this war. Reports say stocks could be exhausted within days if Iranian salvos continue at high intensity because defending against each incoming missile typically consumes multiple interceptors. That means supply is being used faster than it can be replaced.
Iran, by contrast, is understood to still have thousands of missiles, cruise missiles, short and medium-range ballistic missiles and drones available, and production or reserve stocks that let it sustain launches far longer than Israel and the United States can sustain interception at current rates.
So in an attritional sense the defensive interceptors are harder to sustain than Iran’s ability to keep firing offensive missiles in large numbers. But whether that actually happens depends on strategy, resupply, targeting of launchers, and political decisions by all parties, so it is not as simple as one side will literally “run out first” in isolation.
