Around 500 BC, following the Achaemenid conquest of Mesopotamia under Darius I, Old Aramaic was adopted by the Persians as the "vehicle for written communication between the different regions of the vast Persian empire with its different peoples and languages. The use of a single official language, which modern scholarship has dubbed as Official Aramaic, Imperial Aramaic or Achaemenid Aramaic, can be assumed to have greatly contributed to the astonishing success of the Achaemenid Persians in holding their far-flung empire together for as long as they did."[3]