After 539 BCE, following the Achaemenid conquest of Mesopotamia under Darius I, the Achaemenids adopted the local use of Aramaic. When the Achaemenids extended their rule westward, they adopted this language as the vehicle for written communication between the various regions of the vast empire with its different peoples and languages. The use of a single official language, which modern scholarship has dubbed Official Aramaic or Imperial Aramaic, can be assumed to have greatly contributed to the astonishing success of the Achaemenids in holding their far-flung empire together for as long as they did.[6]