Alexander was a king of Macedon, a state in northern ancient Greece. Born in Pella in 356 BC, Alexander was tutored by Aristotle until the age of 16. By the age of thirty, he had created one of the largest empires of the ancient world, stretching from the Ionian Sea to the Himalayas. Alexander broke the power of Persia in a series of decisive battles, most notably the battles of Issus and Gaugamela. He subsequently overthrew the Persian King Darius III and conquered the entirety of the Persian Empire. At that point, his empire stretched from the Adriatic Sea to the Indus River. Alexander's 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 in the mid-15th century. Alexander became legendary as a classical hero in the mold of Achilles, and he features prominently in the history and myth of Greek and non-Greek cultures. He became the measure against which military leaders compared themselves, and military academies throughout the world still teach his tactics.