Xerxes was the son of Darius I and Atossa, daughter of Cyrus I. When Xerxes succeeded his father, Egypt was already in revolt and troubles soon broke out in Babylon; further, there was still pending the matter of the Greeks, where the Persian defeat at Marathon called for vengeance. He crushed the revolts in both Egypt and Babylon with great severity, not sparing even gods, and then turned to the conquest of Greece.
The superiority of the Greek infantry, man for man, was by then well known, but Xerxes’ force outnumbered the Greeks, and he decided to make a land invasion around the northern end of the Aegean. Enormous preparations were made all the way to the borders of Greece. There could be no secrecy, but with overwhelming strength surprise was unnecessary. The Greek historian Herodotus numbered Xerxes’ army in the millions, but 300.000 is a frequent modern estimate. The Greeks responded with a “pan-Helenic” league for defense. Though by no means all the states actually joined, even those that did found it easier to propose plans than to get them agreed on.
In the spring of 480 BC Xerxes advanced, and the Greeks finally sent 10.000 men under the Spartan king Leonidas to block the Pass of Thermopylae. A fleet was sent to Artemisium at the northeastern tip of Euboea to keep the Persians from turning the Pass by the sea. After several days of heroic resistance, the Greeks were defeated when a traitor led a picked Persian force by a mountain track around the Pass, laying central Greece open to the Persians. The Greek fleet withdrew to Salamis off Athens.
Xerxes occupied and then burned Athens. What should the Greek fleet do? The army was fortifying a wall across the Isthmus of Corinth to protect the Peloponnesus (southern Greece), and most of the commanders wanted to withdraw to the Isthmus to prevent a Persian landing south of the wall. The Athenian naval leader, Themistocles, however, wanted to fight in the narrow Bay of Salamis, where Persian numbers would not count. He sent a secret letter to Xerxes promising that if the Persians attacked the Athenians would desert to them in return for the restoration of Athens. Xerxes sent in his fleet but the Athenians did not desert, and Xerxes watched the Greeks win a great victory at Salamis.
Xerxes returned to Asia—not in the flight the Greeks later loved to picture but to protect his communications—leaving his general Mardonius with a still large force to complete the conquest. In 479 BC Mardonius was defeated and killed at Plataea, and the Persian army disintegrated. Greece was free.
The war dragged on, chiefly a naval affair with Athens leading, until the Persians were cleared from Europe and the coasts of the Aegean, but Xerxes took no further part in it. He retired to his capitals and spent the remainder of his reign building, particularly at Persepolis. He became a drunken, embittered man, a pawn of his scheming courtiers, and was murdered in Susa by the captain of the guards.