The same sources also narrate that the Pechenegs made regular raids against their neighbors, in particular against the Khazars and the latter's vassals, the Burtas, and sold their captives. The Khazars made an alliance with the Ouzes against the Pechenegs and attacked them from two directions. Outnumbered by the enemy, the Pechenegs were forced into a new westward migration. They marched across the Khazar Khaganate, invaded the dwelling places of the Hungarians, and expelled them from the lands along the Kuban River and the upper course of the river Donets. There is no consensual date for this second migration of the Pechenegs: Pritsak argues that it took place around 830, but Kristó suggests that it could hardly occur before the 850s.