This place was not very favorably situated, being on the right bank of the Tigris, which is a far less fertile region than the left, and not being naturally a place of any great strength.  The Assyrian territory did not at this time, it is probable, extend very far to the north:  at any rate, no need was as yet felt for a second city higher up the Tigris valley, much less for a transfer of the seat of government in that direction.  Calah was certainly, and Nineveh probably, not yet built; but still the kingdom had obtained a name among the nations; the term Assyria was applied geographically to the whole valley of the middle Tigris; and a prophetic eye could see in the hitherto quiescent power the nation fated to send expeditions into Palestine, and to bear off its inhabitants into captivity.

Shahnaneser I. (ab.  B.C. 1320) is chiefly known in Assyrian history as the founder of Calah (Nimrud), the second, apparently, of those great cities which the Assyrian monarchs delighted to build and embellish.  This foundation would of itself be sufficient to imply the growth of Assyria in his time towards the north, and would also mark its full establishment as the dominant power on the left as well as the right bank of the Tigris.  Calah was very advantageously situated in a region of great fertility and of much natural strength, being protected on one side by the Tigris, and on the other by the Shor-Derreh torrent, while the Greater Zab further defended it at the distance of a few miles on the south and south-east, and the Khazr or Ghazr-Su on the north east.  Its settlement must have secured to the Assyrians the undisturbed possession of the fruitful and important district between the Tigris and the mountains, the Aturia or Assyria Proper of later times, which ultimately became the great metropolitan region in which almost all the chief towns were situated.

It is quite in accordance with this erection of a sort of second capital, further to the north than the old one, to find, as we do, by the inscriptions of Asshur-izir-pal, that Shalmaneser undertook expeditions against the tribes on the upper Tigris, and even founded cities in those parts, which he colonized with settlers brought from a distance.  We do not know what the exact bounds of Assyria towards the north were before his time, but there can be no doubt that he advanced them; and he is thus entitled to the distinction of being the first known Assyrian conqueror.

With Tiglathi-Nin, the son and successor of Shalmaneser I., the spirit of conquest displayed itself in a more signal and striking manner.  The probable date of this monarch has already been shown to synchronize closely with the time assigned by Berosus to the connnencement of his sixth Babylonian dynasty, and by Herodotus to the beginning of his Assyrian Empire.  Now Tiglathi-Nin appears in the Inscriptions as the prince who first aspired to transfer to Assyria the supremacy hitherto exercised, or at any rate claimed, by Babylon.