Instead of pursuing the fleeing Persians after two decisive victories in Asia Minor (the first at the Granicus River; the second on the Plain of Issus, where a great Persian army estimated at half a million met utter defeat), Alexander turned his attention to the island city of Tyre.

Looking eastward, Alexander returned from Egypt through Palestine, and with 47,000 men, overpowered a vast reorganized Persian army near Gaugamela. In quick succession Darius III was murdered by onetime friends, Babylon surrendered, and Alexander pushed on to secure Susa and Persepolis.