The paper deals with Hittite-Assyrian relations under Tukulti-Ninurta and his successor (whose reign ended approximately at the moment when the Hittite kingdom was destroyed by the end of 1190s, according to the middle chronology). The author assumes that: 1) the socalled «Nihriya war» (R⁄ 34.165 and KBo IV 14) is to be dated to the reign of Shalmaneser I; 2) Arnuwanda’s treaty with Ismerikka (CTH 133) must be ascribed to Arnuwanda III and treated as a testimony of Hittite control over the Western part of Hanigalbat under that king; 3) the letter KBo XVIII 25 refers to some territorial concessions made by Tukulti-Ninurta (who is to be identified as father of the letter’s addressee) to the Hittites in Hanigalbat. On the whole it seems that Tukulti-Ninurta mantained peace and «brotherhood» with the Hittites during almost all of his reign; but by its end the Hittites compelled him, either by peaceful or by military means, to give them up some part of Hanigalbat, and their control over that part is reflected in the «Ismerikka Treaty».