The Berke–Hulagu war was fought between two Mongol leaders, Berke Khan of the Golden Horde and Hulagu Khan of the Ilkhanate. It was fought mostly in the Caucasus mountains area in the 1260s after the destruction of Baghdad in 1258. The war overlaps with the Toluid Civil War in the Mongol Empire between two members of the Tolui family line, Kublai Khan and Ariq Böke, who both claimed the title of Great Khan (Khagan). Kublai allied with Hulagu, while Ariq Böke sided with Berke. Hulagu headed to Mongolia for the election of a new Khagan to succeed Möngke Khan, but the loss of the Battle of Ain Jalut to the Mamluks forced him to withdraw back to the Middle East. The Mamluk victory emboldened Berke to invade the Ilkhanate. The Berke–Hulagu war and the Toluid Civil War as well as the subsequent Kaidu–Kublai war marked a key moment in the fragmentation of the Mongol empire after the death of Möngke, the fourth Great Khan of the Mongol Empire.