While Leonidas had been fighting at Thermopylae, the Greek fleet had also been engaged with the Persians at Artemisium. The Persian fleet set sail from the gulf of Therma, and arrived in one day at almost the southern corner of Magnesia. In this position they were overtaken by a sudden hurricane, which blew upon the shore with irresistible fury. For three days and three nights the tempest raged without intermission; and when calm at length returned, the shore was seen strewed for many miles with wrecks and corpses. At least four hundred ships of war were destroyed, together with a countless number of transports, stores, and treasures. The Greek fleet had been seized with a panic terror at the approach of the Persians, and retreated to Chalcis in the narrowest part of the Euboean straits; but upon hearing of the disaster of the Persian fleet, they took courage, and sailed back with the utmost speed to their former station at Artemisium. Being now encouraged to attack the enemy, they gained some success. On the following night another terrific storm burst upon the Persians. All night long it blew upon the Thessalian coast at Aphetae, where the Persian ships were stationed, thus causing little inconvenience to the Greeks upon the opposite shore. Notwithstanding these losses, the Persian fleet still had a vast superiority of numbers, and determined to offer battle to the Greeks. Quitting the Thessalian coast, they sailed towards Artemisium in the form of a crescent. The Greeks kept near the shore, to prevent the Persians from bringing their whole fleet into action. The battle raged furiously the whole day, and each side fought with determined valour. Both parties suffered severely; and though the Persians lost a greater number of ships and men, yet so many of the Greek vessels were disabled that they found it would be impossible to renew the combat. Under these circumstances the Greek commanders saw that it would be necessary to retreat; and their determination was hastened by the news which they now received, that Leonidas and his companions had fallen, and that Xerxes was master of the pass of Thermopylae. Having sailed through the Euboean strait, the fleet doubled the promontory of Sunium, and did not stop till it reached the island of Salamis.