In the year 859 it recounts one of those situations where that's exactly what happens in the absence of any sort of federal law enforcement authority. The people just take matters into their own hands and face up to the Danes as they're called. In Neil Price's book he mentions that sometimes the Danes would make this sort of deal taking the money then share it or combine with the group that they were supposed to attack but both turn their forces on the very people who paid them. They used to call this era in human history the dark ages they don't anymore for obvious reasons.