Alexander III of Macedon known as Alexander the Great was an Ancient Greek king of Macedon. Alexander was one of the most successful military commanders of all time and it is presumed that he was undefeated in battle. By the time of his death at the age 32 he had conquered the Achaemenid Persian Empire adding it to Macedon's European territories; according to some modern writers this was much of the world then known to the ancient Greeks.