U.S. forces struck Iranian rocket launchers on the Strait of Hormuz in their first military action in a month on Sunday, breaking a lull in fighting during an intermittent war that has lasted more than six months.

Vowing to retaliate for what it called a deadly attack, Iran later said it had launched missiles at U.S. sites in Jordan.

Forces with the Revolutionary Guard Corps were observed preparing to launch rockets with sea mines into the strait, according to Tim Hawkins, a spokesperson for the U.S. Central Command.