Baldwin II had made an alliance with some Cumans under their leaders Saronius and Jonas by 1239. It seems likely that he was giving shelter to Cumans fleeing the Mongols. The same act of giving shelter to the Mongols' Cuman enemies was the pretext for the Mongol invasion of Hungary, and probably also for the invasion of Bulgaria. It is likely that the attack on the Latin Empire resulted from the same motive: to punish the protectors of the Cumans.