Themistocles began his political career after the battle of Marathon and the retreat of the Persians. He believed that the Persians would return and proposed to build a strong fleet to meet them at sea. This was opposed by Aristides, the leader of Athens.

Themistocles' naval strategy prevailed and Aristides was banished. When the Persians returned, they defeated the Spartans at Thermopylae and occupied Athens.

Themistocles had moved the Athenians to the island of Salamis, where he engaged and destroyed the Persian fleet.

Themistocles had made Athens a great power but the people believed that he had accepted bribes, and in 471 BC he was banished from the city.