According to Herodotus, Xerxes waited four days before attacking the Greek defenders at Thermopylae.
The Persian king had expected the small Greek force to lose courage and withdraw when confronted by his much larger army. During this pause, Xerxes sent an envoy to demand that the Greeks surrender their weapons. Leonidas rejected the demand, traditionally answering, “Come and take them.”
The attack began on the fifth day after the Persian army arrived. Xerxes first sent Medes and Cissians against the pass, but the narrow terrain allowed the Greek hoplites to fight in a compact formation that neutralized Persia’s numerical advantage. The battle itself lasted three days, even though the waiting period before the first assault lasted four.
A common mix-up is to count the battle’s three fighting days as the entire confrontation. Herodotus’s account distinguishes the four-day delay from the subsequent three-day battle, which ended after Ephialtes revealed the mountain path around the Greek position.