In 1400, the Mongol-Turkic leader Tamerlane captured the city again from the Mamluks. He massacred many of the inhabitants, ordering the building of a tower of 20,000 skulls outside the city. After the withdrawal of the Mongols, all the Muslim population returned to Aleppo. On the other hand, Christians who left the city during the Mongol invasion, were unable to resettle back in their own quarter in the old town, a fact that led them to establish a new neighbourhood in 1420, built at the northern suburbs of Aleppo outside the city walls, to become known as "al-Jdeydeh" quarter ("new district" ).