The fullest account, that of Herodotus, does not begin with three hundred men alone. The Greeks choose Thermopylae to close the land route while their fleet moves to Artemisium. Leonidas arrives with an advance force from several cities, restores the Phocian Wall, and leaves one thousand Phocians to guard the upper path. The ancient shoreline, marshes, and slopes restrict the front; Greek units can rotate and Persian waves cannot employ their full mass at once. After four days of waiting, assaults by the Medes, Cissians, and then the Immortals fail over two days. Intelligence produces the break: Ephialtes guides Hydarnes along Anopaia, the Phocian guard is surprised at dawn, and the rear route is no longer secure. Most Greeks leave; Spartans, Thespians, and Thebans remain for a final battle that the sources do not recount in the same way. Persian victory opens the road but does not decide the war by itself.