In 499 B.C. the Greek cities of Ionia rebelled against Persian rule. The Persian king, Darius, crushed the revolt and sacked Miletus. Darius invaded Greece to punish Athens for the support of the failed revolt in Ionia. A first Persian invasion failed when the Persian fleet was destroyed in a storm off Mount Athos. A second expedition was decisively beaten by the Athenians and their allies on land at the Battle of Marathon in 490 BC.

Xerxes, Darius' son and successor, launched a third expedition on a massive scale on land and sea. To avoid the risk of losing the fleet in a storm Xerxes ordered a canal to be dug through the Athos peninsula, a notoriously stormy area. As the army advanced along the Thracian coast Persian diplomats attempted to persuade the Greeks to submit. Many cities and the Greek oracle at Delphi decided to accept Persian terms, but some twenty cities, under the leadership of Sparta, refused to yield.

On August, 480 B.C., 300 Spartans and 5 600 other warriors died at Thermoplylae in a vain attempt to stop the Persian advance. Then, as Xerxes' army marched south, the Athenians were compelled to evacuate the city, which was burned by the Persians.

Yet the Persians had difficulty in supplying their army and Xerxes decided to attack the Greek fleet, which had taken refuge in the Strait of Salamis near Athens. In the narrow Strait, the superior Persian fleet became disorganised and the Greeks, by skillful maneuvering, were able to win a decisive victory. Xerxes ordered an immediate retreat to prevent his army from being trapped.

A token army was left in Greece but this force was destroyed the following year at the Battle of Plataea. After this defeat the Persians abandoned their expansionist aims and the independence of Greek civilization was secured.