The battle took place simultaneously with the naval battle at Artemisium. It was held at the narrow coastal pass of Thermopylae ("The Hot Gates") in August or September 480 BC. The Persian invasion was a delayed response to the defeat of the first Persian invasion of Greece, which had been ended by the Athenian victory at the Battle of Marathon in 490 BC. By 480 BC, Xerxes had amassed a massive army and navy and set out to conquer all of Greece. The Athenian politician and general Themistocles had proposed that the allied Greeks block the advance of the Persian army at the pass of Thermopylae, while simultaneously blocking the Persian navy at the Straits of Artemisium.