section_path: Conquest of the Achaemenid Persian Empire/Assyria and Babylonia
section_name: Assyria and Babylonia
paragraph_text: Assyria and Babylonia
  
  Leaving Egypt in 331 BC, Alexander marched eastward into Achaemenid Assyria in Upper Mesopotamia (now northern Iraq) and defeated Darius again at the Battle of Gaugamela. Darius once more fled the field, and Alexander chased him as far as Arbela. Gaugamela would be the final and decisive encounter between the two. Darius fled over the mountains to Ecbatana (modern Hamadan) while Alexander captured Babylon.
  
  Babylonian astronomical diaries say that "the king of the world, Alexander" sent his scouts with a message to the people of Babylon before entering the city: "I shall not enter your houses".