By 480 BC, Xerxes had amassed a massive army and navy and set out to conquer all of Greece. 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. It was held at the narrow coastal pass of Thermopylae ('The Hot Gates') in August or September 480 BC. The battle took place simultaneously with the naval battle at Artemisium.
It was fought in 480 BC over the course of three days, during the second Persian invasion of Greece.
The Battle of Thermopylae ( / θ ər ˈ m ɒ p ɪ l iː/ thər- MOP-i-lee Greek: Μάχη τῶν Θερμοπυλῶν, Máchē tōn Thermopylōn) was fought between an alliance of Ancient Greek city-states, led by King Leonidas I of Sparta, and the Achaemenid Empire of Xerxes I.
