Map of the Empire of Alexander the Great. Alexander became king of the Greek kingdom of Macedon in 336 BC at the age of 20. This map shows the route (grey) of his journey eastwards as he conquered the Persian Empire, and the extent of the Greek Empire (dark orange) at Alexander's death in 323 BC. Alexander started his military campaign in 334 BC, marching east from Macedonia through western Asia Minor. By 332 BC Alexander had won battles throughout Asia Minor, the Levant and Syria, and reached Egypt. In 331 BC Alexander marched through Mesopotamia, where he defeated the Persian king Darius III for the final time and declared himself King of Persia in 330 BC. He then marched east through Persia, reaching modern day Afghanistan and India before returning home.