The Viking Art of War

Part of their strategic problem was the scarcity and even unreliability of their shipping. They had an essentially coastal rather than oceanic navy, and their manpower was limited. For most of the high Viking era they could field only one 'Great Army' at a time, and had to be content with relatively minor raiding operations elsewhere. Nevertheless, the appearance of even few highly-motivated Vikings in an area without good coastal defence could often spread.