sentences:  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.