The global arms race to defend against Iran’s missile and drone attacks is exposing a critical shortage of advanced defense systems, with the United States and its allies facing a growing risk of running out of interceptors in the midst of the ongoing conflict. President Donald Trump has suggested that the US-Israeli air campaign against Iran will continue until the regime ‘cries uncle’ or ‘can’t fight any longer.’ Meanwhile, Iran’s foreign minister has declared that his country will fight ‘as long as it takes’ and has shown little interest in negotiating a ceasefire. However, the question of whether the war can continue is not just a matter of will, but of material capability — and the world may not have enough ammunition to sustain it.

The Cost of Missile Defense

The United States has already burned through an estimated $2.4 billion worth of Patriot interceptors in just the first five days of the conflict, with each interceptor costing around $4 million. These systems, designed to intercept ballistic missiles, are among the most sophisticated and expensive in the world. Similarly, the U.S. used around a quarter of its total stock of THAAD interceptors during last June’s conflict, and with only 11 of these interceptors produced annually, the strain on global supply chains is becoming evident.

Sam Lair of the James Martin Center for Nonproliferation Studies warned that the cost of missile defense is a critical factor in modern warfare. ‘You’re on the wrong side of the cost curve if you’re doing missile defense in the first place,’ he said. ‘That’s just the reality of how these types of wars work. Interceptors are expensive, they don’t have very many of them, and not many of them are produced each year.’

The demand for interceptors is not only coming from the Middle East. European officials have confirmed that interceptors needed for the war in Ukraine are being diverted to the Middle East, highlighting the global nature of the arms race. In a sign of the urgency, the U.S. is reportedly moving parts of a powerful THAAD system from South Korea to the Middle East at the same time North Korea is test-firing missiles from its newest warship.

Iran’s Offensive and the Limits of Its Arsenal

Iran has launched thousands of missiles and one-way attack drones at 13 countries, killing at least 43 people, including seven U.S. servicemembers, according to data from the Israeli think tank INSS. These attacks have targeted a wide range of locations, from U.S. military bases to luxury hotels in Dubai to Amazon data centers. Recently, three ships transiting the Strait of Hormuz were attacked, as part of Iran’s strategy to disrupt global oil exports through this critical chokepoint of the world energy market.

Despite the scale of Iran’s attacks, the damage has been mitigated by the strong defensive capabilities of its targets. Most of the countries attacked have successfully intercepted over 90 percent of the projectiles fired at them. However, the cost of maintaining these defenses is immense. The U.S. has already used a significant portion of its limited stock of interceptors, and the replacement rate of these weapons is far from matching the current demand.

MacKenzie Eaglen of the American Enterprise Institute noted that the U.S. may need years to replenish its stocks of Tomahawk missiles, which are essential for long-range precision strikes. ‘For years, all of the services have been firing precision stocks much faster than their replacement rates,’ she said. ‘This is a problem that has been building up over time and is now coming to a head.’

The Decline of Iran’s Missile Capabilities

The heavy bombardment of Iran’s missile facilities by the U.S. and Israel has taken a toll on its ability to launch attacks. According to the U.S. military, the number of Iranian missile launches is down 90 percent, and drone launches are down 83 percent since the start of the conflict. Secretary of Defense Pete Hegseth called this ‘strong evidence of degradation.’ Some experts believe the drop in launches is due to Iran holding back part of its arsenal, anticipating a prolonged conflict.

Iran’s missile stockpile was previously estimated to be between 2,000 and 3,000 missiles. During last June’s conflict, Iran fired around 600 of these missiles, with many more destroyed on the ground by Israeli airstrikes. However, Iranian authorities have been working to replenish their stockpiles and harden their defenses. Much of this stockpile was concentrated in vast underground ‘missile cities,’ which have been heavily targeted in the early phase of the war.

Israel estimates that it has destroyed or buried around 70 percent of Iran’s missile launchers. Even if these estimates are on the high side, the speed at which the U.S. and Israel have been able to dismantle much of Iran’s once-feared missile deterrent has surprised many observers. The use of bunker buster bombs to destroy the entrances to these missile cities has left hundreds of missiles buried underground, rendering them inoperable.

Iran has also been a pioneer in the development of one-way attack drones, particularly the low-cost ‘Shahed’ model, which has been used extensively by Russian forces in the war in Ukraine. The U.S. is now deploying its own drone closely modeled on the Shahed. However, the exact size of Iran’s drone stockpile is unknown, and production capacity has likely declined since the war began.

The goal of Iran’s leaders is not to defeat the U.S. and Israel, as that has never been in question. Instead, they aim to continue inflicting pain to the point where Trump, facing skyrocketing gas prices, a jittery economy, falling poll numbers, and grumbling allies, decides to call it quits and resist calls to renew the war later. This strategy has been complicated by the damage inflicted on the command structure of Iran’s Major Guard Corps (IRGC), which has led to a more decentralized and unpredictable pattern of attacks.

Iran’s choice of targets has been somewhat unexpected, with more projectiles directed against Gulf states than Israel. Analysts suggest this may be due to the damage inflicted on the IRGC’s command structure, which has resulted in missile commanders making their own decisions on where to launch. ‘It was 30 different IRGC commanders doing their own thing, and that’s why we saw them doing things like launching against Oman, which made no sense to anybody,’ said Decker Eveleth of the Center for Naval Analyses.

Iran may also be targeting the Gulf states because those are the missiles it still has available. It used many of its longer-range weapons to strike Israel during the 12-day war, while its shorter-range missiles, aimed primarily at the Gulf and U.S. bases in the region, were relatively untouched and not as heavily bombed in the early days of the conflict. This suggests that Iran is carefully managing its remaining arsenal to sustain the war as long as possible.