The main misconception about Vikings, and it's one that shows up continuously on neo-Pagan fanwank Facebook pages, is that they were fearless, unparallelled warriors who never backed down from a fight and were bound by strict chivalric honour codes.

In reality, one of the main reasons that the Vikings were such successful raiders is because they ran away from fights all the time. Viking strategy revolved around speed and mobility, manouevring around larger forces and avoiding fighting as much as possible to strike at undefended or poorly defended targets, to overwhelm local forces piecemeal with local numerical superiority and flee when larger garrisons arrive. This destroys morale and also forces any defender to tie up large amounts of manpower trying to fight off a hundred different threats.

Later English tactics against the Vikings work because they're expressly designed to curtain the Vikings ability to manouevre, to block escape routes and quickly dispatch reinforcements to force the Vikings into battle where they could be destroyed.

Needless to say, honour and chivalry are odd concepts to apply to groups that would purposely target undefended religious sites, carry off slaves and steal anything going.