 The Mongol invasion of Europe ended in 1242 , in part because of the death of the Great Khan Ögedei , successor to Genghis Khan . When one Great Khan died , Mongols from all parts of the empire were recalled to the capital to decide who should be the next Great Khan . In the meantime , the Mongols ' relentless march westward had displaced the Khawarizmi Turks , who themselves moved west , eventually allying with the Ayyubid Muslims in Egypt . Along the way , the Turks took Jerusalem from the Christians in 1244 . After the subsequent loss at the Battle of La Forbie , Christian kings began to prepare for a new crusade ( the Seventh Crusade ) , declared by Pope Innocent IV in June 1245 at the First Council of Lyon . The loss of Jerusalem caused some Europeans to look to the Mongols as potential allies of Christendom , provided the Mongols could be converted to Western Christianity . In March 1245 , Pope Innocent IV had issued multiple papal bulls , some of which were sent with an envoy , the Franciscan John of Plano Carpini , to the " Emperor of the Tartars " . In a letter now called the Cum non solum , Pope Innocent expressed a desire for peace , and asked the Mongol ruler to become a Christian and to stop killing Christians . However , the new Mongol Great Khan Güyük , installed at Karakorum in 1246 , replied only with a demand for the submission of the pope , and a visit from the rulers of the West in homage to Mongol power : 
