The Persian advance was blocked at the pass of Thermopylae by a small Allied force under King Leonidas I of Sparta; simultaneously, the Persian fleet was blocked by an Allied fleet at the straits of Artemisium. At the famous Battle of Thermopylae, the Allied army held back the Persian army for seven days, before they were outflanked by a mountain path and the Allied rearguard was trapped and annihilated. The Allied fleet had also withstood two days of Persian attacks at the Battle of Artemisium, but when news reached them of the disaster at Thermopylae, they withdrew to Salamis.