Why did law and order break down in Europe after the fall of Rome?

The breakdown of Law and Order was a problem of the Carolingian empire which was established by Charlemagne in 800, some 300 years after the fall of the western part of the Roman Empire. This was due to the problem of succession. Following Frankish custom, the empire was partitioned among the sons of the dead emperor. This repeatedly led to wars between the sons, in which other close relatives also got involved. It created a complex web of wars around most of the empire. The constant state of war led to the breakdown of central power and law and order, the rise of feudalism and the fall of the Carolingian empire 88 years later.