Kitbuqa was killed. Palestine and Syria were regained, the border remaining the Tigris for the duration of Hulagu's dynasty. Berke's vow of vengeance against Hulagu had to wait until the latter's return to his lands after the death of Möngke Khan. Hulagu returned to his lands by 1262, but instead of being able to avenge his defeats, was drawn into civil war with Berke and the Blue Horde. Berke Khan had promised such a defeat in his rage after Hulagu's sack of Baghdad. Muslim historian Rashid-al-Din Hamadani quoted Berke Khan as telling his Mongols and Muslim subjects, in protest at the attack on Baghdad: "He (Hulagu) has sacked all the cities of the Muslims, and has brought about the death of the Caliph. With the help of God I will call him to account for so much innocent blood." (see The Mongol Warlords, quoting Rashid al-Din's record of Berke Khan's pronouncement; this quote is also found in The Mamluk-Ilkhanid War) Before his succession, he also complained to Batu "We helped Möngke to enthrone. But he forgot who the enemy is or friend is. Now, he is starving the lands of our friend Caliph. It is abject". It is notable that Berke Khan kept his promise, allying himself with the Mamluks, (Berke sought an alliance with the Mamluk sultan Baibars against Hulagu) and when Hulagu returned to his lands in 1262, after the succession was finally settled with Kublai as the last Great Khan, and massed his armies to avenge Ain Jalut and attack the Mamluks, Berke Khan initiated a series of raids in force which drew Hulagu north to meet him. This was the first open conflict between Mongols, and signalled the end of the unified empire. In retaliation for these attacks, Berke and Hulagu slaughtered each other's ortogh merchants. But the reasons for the conflict between Berke and Hulagu were both religious and territorial. Möngke Khan gave lands in current day Azerbaijan, which had been given to Jochi by Genghis Khan, to his brother Hulagu. Although Berke did not like the situation, he was patient until Möngke's death. Berke at first desisted from fighting Hulagu out of Mongol brotherhood, he said Mongols are killed by Mongol swords. If we were united, then we would have conquered all of the world. but the economic situation of the Golden Horde due to the actions of the Ilkhanate led him to declare