Summary: At 18, Alexander had conquered mainland Greece; at 20, he was crowned King of Macedonia; and by 26, he had made himself master of the once mighty Persian Empire. By the time of his death in 323 BC, aged only 33, he was ruler of the known world and was being worshipped as a god by the Greeks, both at Babylon, where he died, and among the Greek cities of the Asiatic seaboard, further west.