In September 1260, the Egyptian Mamluks negotiated for a treaty with the Franks of Acre which allowed them to pass through Crusader territory unmolested, and engaged the Mongols at the Battle of Ain Jalut on 3 September 1260. The Mamluks won a decisive victory, killing the Mongols' Nestorian Christian general Kitbuqa, and five days later they had retaken Damascus. Aleppo was recovered by the Muslims within a month, and a Mamluk governor placed to govern the city. Hulagu sent troops to try to recover Aleppo in December. They were able to massacre a large number of Muslims in retaliation for the death of Kitbuqa, but after a fortnight could make no other progress and had to retreat.