Mesopotamia, the name given after Alexander the Great's time to the territory "between the rivers" Euphrates and Tigris, stretching from Babylonia NW. to the Armenian mountains; under irrigation it was very fertile, but is now little cultivated; once the scene of high civilisation when Nineveh ruled it; it passed from Assyrian hands successively to Babylonian, Persian, Greek, Roman, and Arab; now, after many vicissitudes, it is in the deathly grasp of Turkish rule.