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.