In 483 a rich vein of silver was discovered at Laurion, near Athens. Its estimated value was 100 Talents, roughly equivalent to 100 million dollars in modern money. Normal procedure would be to mine the silver and divide the spoils equally among the citizenry.
Themistocles had other ideas. For some time he had warned that the Persians still remained a threat, as did those city-states, like nearby Aegina, who had taken the Persian side in the war. Themistocles now argued that this newly found windfall be devoted to building a navy.
The assembly split in two factions. Conservatives, represented by Aristides, argued against Themistocles, convinced that the Athenians should stick with what they knew: land-based infantry warfare. Radicals, mainly made up of poorer citizens, sided with Themistocles believing the building of a fleet would not only make Athens a great sea power, but provide them with jobs building the ships!
A vote on ostracism was to decide the outcome.
Ultimately, the Athenians sided with Themistocles and Aristides went into exile. Immediately work began at break neck speed to build a navy of 200 triremes, the most advanced ships of the Ancient World.
But time was running out...
The Persians Invade - Thermopylae