Nine years after the Greek cities rebelled from the Persian empire, the Persian ruler, Darius, started a series of wars called the Persian Wars. Darius and his army sailed to Marathon, where the Athenians defeated the Persian army.
Ten years later, Xerxes, Darius's son, took power. He also tried to conquer Greece. The Persians battled the Spartans in Thermopylae, and succeeded when a traitorous Greek told the Persian army to attack from behind the Spartans in the mountain pass.
The Greeks however quickly devised a plan. The Athenians navy led the Persian ships into the straits of Salamis. The Persian navy's boats got stuck in the strait and the small Athenian boats sank the Persian ships, winning the battle.