Simultaneous with the battle at Thermopylae, an Allied naval force of 271 triremes defended the Straits of Artemisium against the Persians, thus protecting the flank of the forces at Thermopylae. Here the Allied fleet held off the Persians for three days; however, on the third evening the Allies received news of the fate of Leonidas and the Allied troops at Thermopylae. Since the Allied fleet was badly damaged, and since it no longer needed to defend the flank of Thermopylae, the Allies retreated from Artemisium to the island of Salamis.