The city of Bukhara was not heavily fortified, with a moat and a single wall, and the citadel typical of Khwarezmi cities. The city leaders opened the gates to the Mongols, though a unit of Turkish defenders held the city's citadel for another twelve days. Survivors from the citadel were executed, artisans and craftsmen were sent back to Mongolia, young men who had not fought were drafted into the Mongolian army and the rest of the population was sent into slavery. As the Mongol soldiers looted the city, a fire broke out, razing most of the city to the ground. Genghis Khan had the city's surviving population assemble in the main mosque of the town, where he declared that he was the flail of God, sent to punish them for their sins.