Inspired in part by the recent popularity of the Vikings television series, the History Channel recently published a series of in-depth articles about the Viking people and their conquests. One piece discussed Ireland's remarkable survival against Viking invasions at a time when the warriors dominated the region.
According to History Channel scholars, Vikings used Ireland, and specifically Dublin, as a source of slaves. They systematically visited the island for years, acquiring and trading slaves and raiding monasteries.
Despite the repeated invasions, Ireland never completely fell to the Vikings. This may have been due to Ireland's tradition of decentralized power. The island nation had 150 local kingdoms and a dozen over-kingdoms, making it difficult to broker peace or control a majority of the land. Killing one king had little impact between his many successors and the many neighboring kings who held just as much power.
This potential weakness turned out to be an effective defense against Vikings. They could not seize power, so they took what they could and left. Norse influence remains apparent in parts of Ireland, but the nation never completely succumbed to its invaders.