After Batu Khan returned from Mongolia, his relations with his cousins were so poor that not until the election of Möngke Khan as Khagan did he again consider turning westward to Europe. However, he died in 1255 before those plans could be put into motion. Under the rule of his brother Berke, the Golden Horde was preoccupied with the conflict with their cousins in the Ilkhanate, led by Hulagu Khan, whom Berke Khan despised for the Battle of Baghdad and the murder of Caliph Al-Musta'sim.