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.

the alfred thayer mahan award for literary achievement is awarded each year by the navy league of the united states. the award is named for an american naval historian and theorist, rear admiral alfred thayer mahan, united states navy who, through his writing, provided stimulus and guidance to those who share in the defense of the nation. presented since 1957, "this award for literary achievement is awarded to a u.s. navy officer, u.s. marine corps officer, enlisted service member, or civilian who has made a notable literary contribution that has advanced the knowledge of the importance of sea power in the united states."[1]