Alexander III of Macedon commonly known as Alexander the Great, was a king of Macedon, a state in northern Greece. By the age of thirty, he had created one of the largest empires in ancient history, stretching from the Ionian Sea to the Himalayas. He was undefeated in battle and is considered one of the most successful commanders of all time. Born in Pella in 356 BC, Alexander was tutored by the famed philosopher Aristotle. In 336 BC he succeeded his father Philip II of Macedon to the throne after Philip was assassinated. Philip had brought most of the city-states of mainland Greece under Macedonian hegemony, using both military and diplomatic means.
Upon Philip's 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. In 334 BC he invaded Persian-ruled Asia Minor and began a series of campaigns lasting ten years. Alexander broke the power of Persia in a series of decisive battles, most notably the battles of Issus and Gaugamela. Subsequently he overthrew the Persian king Darius III and conquered the entirety of the Persian Empire. The Macedonian Empire at that point stretched from the Adriatic Sea to the Indus River.
Following his desire to reach the "ends of the world and the Great Outer Sea", he invaded India in 326 BC, but was eventually forced to turn back by the near-mutiny of his troops. Alexander died in Babylon in 323 BC, without realizing a series of planned campaigns that would have begun with an invasion of Arabia. In the years following Alexander's death a series of civil wars tore his empire apart which resulted in the formation of a number of states ruled by the Diadochi – Alexander's surviving generals. Although he is mostly remembered for his vast conquests, Alexander's lasting legacy was not his reign, but the cultural diffusion his conquests engendered.
Alexander founded some twenty cities that bore his name. His settlement of Greek colonists and the resulting spread of Greek culture in the east resulted in a new Hellenistic civilization, aspects of which were still evident in the traditions of the Byzantine Empire until the mid-15th century. Alexander became legendary as a classical hero in the mold 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 military academies throughout the world still teach his tactical exploits.