331 BC

Events

Alexander departs from Egypt and leads his forces towards Phoenicia. He leaves Cleomenes of Naucratis as the ruling nomarch to control Egypt.
October 1 — Alexander of Macedonia is victorious in the Battle of Gaugamela (near ancient Ninevah) over the Persian King Darius III. Darius turns his chariot and flees, although his subordinates fight on. Alexander pursues the defeated Persian forces to Arbela, but Darius escapes with his Bactrian cavalry and Greek mercenaries into Media.
Alexander becomes the master of the Persian Empire, ending the Achaemenid dynasty. Babylon and Susa open their gates to him. In the capital, Susa, Alexander gains access to huge treasures amounting to 50,000 gold talents.

While Alexander is fighting in Asia, Agis III of Sparta, profiting from the Macedonian king's absence from Greece, leads some of the Greek cities in a revolt. With Persian money and 8,000 Greek mercenaries, he holds Crete against Macedonian forces. In the Peloponnesus he routes a force under the Macedonian general Coragus and, although Athens stays neutral, he is joined by Elis, Achaea (except Pellene) and Arcadia, with the exception of Megalopolis, the staunchly anti-Spartan capital of Arcadia, which Agis III's forces besiege.

Alexander of Epirus takes Heraclea from the Lucanians, and Terina and Sipontum from the Bruttii.
Tarentum turn against Alexander of Epirus when they realize that he intends to create a kingdom of his own in southern Italy. Alexander is defeated and killed in the Battle of Pandosia on the banks of the Acheron.

The Gallic tribe of the Senones and the Romans conclude a peace and enter upon a period of friendly relations which lasts the rest of the century.