From the river of Egypt to the great river, the river Euphrates (Gen 15:18), all the region west of the Euphrates from Tiphsah to Gaza (1 King 4:24), this is the geographical entity that formed a key satrapy in the Persian Empire. Known as Hatti land or Amurru in Assyrian and Babylonian sources, It was called "Beyond the River" from days of Esarhaddon and this become its official Aramaic name in Persian documents.When Cyrus took Babylon he appointed a governor over "Babylon and Beyond the River" ie the entire chaldean Kingdom. There was also a local governor of "Beyond the River" Tattennai is known to have served from 520 to at least 502 BC "Beyond the river" was an independent satrapy at least by 482 B.C after a serious revolt in Bavel was burtally suppressed.
