The correct answer is - False.
During the peak of the Viking's military power, the kings of the other nations that faced them just weren't able to defend their territories from them. The Vikings were excellent warriors, tall, strong, and had terrifying weaponry. The Vikings were so successful in their invasions, that apart from gaining lot of territory, mostly coastal areas (because it suited their lifestyle), there were kings that were actually paying the Viking warriors to protect them from other invaders, or even had a personal guard of Vikings around them, as was the example with Byzantium.