The Battle of Gaugamela Ends the Persian Empire

The event

East of the Tigris River, Alexander met Darius III's main imperial army — vastly larger than his own force — at Gaugamela. Through superior tactics and the discipline of his Macedonian phalanx and cavalry, Alexander won a total and decisive victory. Darius fled the field once more, and was soon murdered by his own officers as they scrambled to distance themselves from a lost cause.

With this battle, the Achaemenid Persian Empire that Cyrus the Great had founded roughly two centuries earlier effectively came to an end. Alexander marched on to occupy Babylon, Susa, and Persepolis in turn, claiming the title 'King of Asia' and inheriting the vast administrative empire that Darius I had built.