The weapon that won the second Persian war was

The trireme. It was a warship propelled by sail for long distances. For combat the sail and mast were taken down, and the ship was propelled by oars, with three rows of oarsmen on each side. Enemy ships were sunk by ramming them. It was a superior ship to those of the Persians, and although the Athenians were badly outnumbered, quality made a difference.