Themistocles was a populist politician who foresaw the Persian threat. Years before the invasion, he convinced Athenians to use silver from a new mine to build a massive fleet of triremes, arguing that Athens' future lay at sea.
His strategy was vindicated at Salamis. By feeding false information to Xerxes, he tricked the Persians into attacking the Greek fleet in a narrow strait, neutralizing their numerical advantage. It was one of the most decisive naval battles in history.
Despite saving Greece, his arrogance made him many enemies. He was ostracized (exiled) from Athens and ended his days as a governor in the Persian Empire, a servant to the son of the king he had defeated.