During the early Middle Ages, the Vikings invasion contributed to the end of which great European empire?

The North Sea Empire

Explanation:

The Viking presence dwindled until 1066, when the invading Norsemen lost their final battle with the English at Stamford Bridge. The death in the battle of King Harald Hardrada of Norway ended any hope of reviving Cnut's North Sea Empire; it is because of this, rather than the Norman conquest, that 1066 is often taken as the end of the Viking Age. Nineteen days later, the Normans, themselves descended from Norsemen, invaded England and defeated the weakened English army at the Battle of Hastings.

"a government in which power is divided between state and national levels". federalism is a system of government in which entities such and state and province, share power with the national government.

answer: (fluidity)is the correct answer.

explanation: because of this characteristic, success on the battlefield depends in large part on the ability to adapt to proactively change events to our advantage as well as to react quickly to constantly changing conditions