Assyria and Elam had hitherto seldom encountered one another on the field of battle. A wide barrier of semi-barbarous states had for a long time held them apart, and they would have had to cross the territory of the Babylonians or the Cossaeans before coming into contact with each other. Tiglath-pileser I., however, had come into conflict with the northern districts of Elam towards the end of the twelfth century B.C., and more recently the campaigns of Assur-nazir-pal, Shalmaneser III., and Ramman-nirari had frequently brought these sovereigns into contact with tribes under the influence of Susa; but the wildness and poverty of the country, and the difficulties it offered to the manoeuvres of large armies, had always prevented the Assyrian generals from advancing far into its mountainous regions.* The annexation of Aramaean territory beyond the Tigris, and the conquest of Babylon by Tiglath-pileser III., at length broke through the barrier and brought the two powers face to face at a point where they could come into conflict without being impeded by almost insurmountable natural obstacles, namely, in the plains of the Umliash and the united basins of the Lower Ulai and the Uknu. Ten years' experience had probably sufficed to convince Khumban-igash of the dangers to which the neighbourhood of the Assyrians exposed his subjects. The vigilant watch which the new-comers kept over their frontier rendered raiding less easy; and if one of the border chieftains were inclined to harry, as of old, an unlucky Babylonian or Cossaean village, he ran the risk of an encounter with a well-armed force, or of being plundered in turn by way of reprisal. * Sargon declares distinctly that Merodach-baladan had invoked the aid of Khumban-igash.