Battle of Gaugamela

Alexander the Great of Macedonia defeated King Darius III of the Persian Achaemenid Empire at Gaugamela near modern Erbil, Iraq, on October 1, 331 BCE. Despite being outnumbered, Alexander used a feigned retreat and cavalry charge to break Persian lines. Darius fled the battlefield, ending his rule. The victory gave Alexander control over Babylon, Susa, Persepolis, and the Persian Empire's western territories, leading to the Achaemenid Empire's collapse.