Despite their successes, the Abbasids hoped to come to terms with the Mongols and by 1241 had adopted the practice of sending an annual tribute to the court of the khagan. Envoys from the Caliph were present at the coronation of Güyük Khan as khagan in 1246 and that of Möngke Khan in 1251. During his brief reign, Güyük insisted that the Caliph Al-Musta'sim fully submit to Mongol rule and come personally to Karakorum. Blame for the Caliph's refusal and for other resistance offered by the Abbasids to increased attempts by the Mongols to extend their power was placed by the khagans on Chormaqan's lieutenant and successor, Baiju.