Assyria as a state ended abruptly. A coalition took Nineveh in 612 BCE and the empire disappeared within a few years, an event the Hebrew prophets celebrate at length. The name did not disappear with it.
Christianity spread early and deeply through northern Mesopotamia, and the churches of the region developed in Syriac, a dialect of Aramaic, largely outside the Roman empire and therefore outside the imperial councils that shaped western and Byzantine doctrine. The Church of the East, based in the Persian empire and later under Islamic rule, held a christology the councils condemned, organised itself under its own patriarch, and ran the most geographically extensive mission of the medieval world, reaching Central Asia, India and China. Monasteries of this tradition produced the scholars who later translated Greek philosophy and medicine into Arabic.
The modern Assyrian identity, taken up in the nineteenth century by Syriac-speaking Christians of the region and connecting them explicitly to the ancient kingdom, belongs to that long church history rather than to unbroken descent from Nineveh, and the connection is debated by historians while being held firmly by the community itself.
The twentieth century emptied much of the homeland. Massacres during the First World War, later displacements, and the destruction and expulsion carried out in the Nineveh plains after 2014 have left the population concentrated in diaspora, with the ancient sites themselves damaged or destroyed.