Qatna was at its apex during the reign of Išḫi-Addu. Mari was conquered by Shamshi-Adad I of Assyria, who appointed his son Yasmah-Adad as its king. Išḫi-Addu was allied with Shamshi-Adad and is attested corresponding with Mari for a period of six years between . At its height, the kingdom extended from the upper valley of the Orontes to Qadeš in the west, while Palmyra was Qatna's easternmost city. It was bordered by Yamhad in the north, while the south was dominated by Hazor, a Qaṭanean vassal. The many kingdoms of Amurru, which controlled the central Levantine coast between Byblos and Ugarit, bordered Qatna from the west and were counted among Išhi-Addu's vassals. Also under the rule of Qatna were various cities in the Beqaa Valley and the cities in the region of Apum, in the modern Damascus Oasis.