 However, a violent storm and harassment by the Thracians forced the troops to return to Persia.Seeking revenge on Athens and Eretria, Darius assembled another army of 20,000 men under his Admiral, Datis, and his nephew Artaphernes, who met success when they captured Eretria and advanced to Marathon.In 490 BCE, at the Battle of Marathon, the Persian army was defeated by a heavily armed Athenian army, with 9,000 men who were supported by 600 Plataeans and 10,000 lightly armed soldiers led by Miltiades.