Philip had brought most of the city-states of mainland Greece under Macedonian hegemony, using both military and diplomatic means. Upon his death, Alexander inherited a strong kingdom and an experienced army. He succeeded in being awarded the generalship of Greece and with his authority firmly established, launched the military plans for expansion left by his father. He invaded Persian-ruled Asia Minor, and began a series of campaigns lasting 10 years. Alexander repeatedly defeated the Persians in battle, marched through Syria, Egypt, Mesopotamia, Persia, and Bactria and in the process he overthrew the Persian king Darius III and conquered the entirety of the Persian Empire.ii[›] Following his desire to reach the "ends of the world and the Great Outer Sea", he invaded India, but was eventually forced to turn back by the near-mutiny of his troops, who had tired of war.

Alexander died in Babylon in 323 BC, before having the chance to realize a series of planned campaigns, beginning with an invasion of Arabia. In the years following Alexander's death, his empire was torn apart in a series of civil wars, which resulted in the formation of a number of states ruled by Macedonian nobility. Remarkable though his conquests were, Alexander's lasting legacy was not his reign, but the cultural diffusion engendered by his conquests. The import of Greek colonists and culture to the east, initiated by Alexander, resulted in a new Hellenistic culture, aspects of which were still evident in the traditions of the Byzantine Empire up until the mid-15th century. Alexander himself became legendary, as a classical hero in the mould of Achilles and features prominently in the history and myth of Greek and non-Greek cultures. He became the measure against which generals, even to this day, compare themselves, and his tactical exploits are still taught in military academies throughout the world.