After the battle at Marathon, Athens felt safe from the Persian threat and did not see the need for further naval expansion. Themistocles, however, was convinced that the Persians would return with even greater force. As proof, he cited the Delphic Oracle, who had foretold that Athens would be protected only by ‘walls of wood’. Themistocles succeeded in persuading the Athenian citizens to use the Laurion silver to finance the construction of 200 triremes, the Classic Greek warship.

The fleet of triremes was based in three different harbours in the Piraeus: Kantharos, today's main ferry hub, had 94 ship-sheds, Mounychia 82, and Zea 196.

The legacy of Themistocles culminated in the naval supremacy of Athens, which peaked during the Second Persian War, and continued until the end of the fifth century BC.