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 group i'm selecting: greeks.

a first group of greek immigrants came to the us in the 1850s. the second group came to america starting in the 1890s due to economic opportunities they didn't have back in their home caused by the hardships of ottoman rule. greek immigration was 90% male, many of them expected to work and return to greece after earning enough capital, but ultimately had to remain in the us after the greek genocide.