Arab states in the Persian Gulf tried to prevent a US-Israeli strike on Iran. Now, as Tehran retaliates, their own territories are under fire.

Iran’s neighbors have spent decades preparing for a potential attack. But the ferocity of Tehran’s retaliation has left both governments and people of the region stunned.

Since the Islamic Republic took power almost half a century ago, oil-rich US-allied Arab states have fortified themselves against their neighbor by spending hundreds of billions of dollars on American weapons and hosting US bases in the hope of deterring an attack. Up to 40,000 American troops are stationed across the region, equipped with advanced US missile-defense systems.

For decades, Iran has protested the presence of US troops across from its shores, repeatedly warning its Arab neighbors that states hosting American military assets could be targeted in the event of a US attack on the country.

Iran’s supreme leader, Ayatollah Ali Khamenei, was killed in an airstrike this week that also took out 49 other top Iranian officials, US President Donald Trump said. US Defense Secretary Pete Hegseth said Monday that Iran’s “nuclear pursuits” and the “swelling arsenal of ballistic missiles and killer drones” are “no longer tolerable.”

As the US military began massing military assets near Iran over the past few weeks, Tehran repeatedly warned that any US attack would not be met with the same “restraint” it showed during last summer’s 12-day war, which started when Israel launched a surprise attack on Iran that eventually drew in the United States.

Still, the response to Khamenei’s killing has triggered a response that few observers expected. The regime has fired more than 400 ballistic missiles and almost 1,000 drones at Arab states along the Persian Gulf since Khamenei’s killing, according to regional governments.

Even more striking was the rapid escalation by the Islamic Revolutionary Guard Corps (IRGC). Tactics once considered a last resort were deployed within the first 72 hours. Urban centers, energy infrastructure, airports and hotels across the gulf’s Arab states were hit, shaking populations long used to their relatively security.