At first Kayqubad sought an alliance with his Turkish kinsman Jalal ad-Din Mingburnu against the Mongol threat. The alliance could not be achieved, and afterwards Jalal ad-Din took the important fortress at Ahlat. Kayqubad finally defeated him at the Battle of Yassıçimen between Sivas and Erzincan in 1230. After his victory, he advanced further east, establishing Seljuq rule over Erzurum, Ahlat and the region of Lake Van (formerly part of Ayyubids). The Artuqids of Diyarbakır and the Ayyubids of Syria recognized his sovereignty. He also captured a number of fortresses in Georgia, whose queen sued for peace and gave her daughter Tamar in marriage to Kayqubad's son, Kaykhusraw II.