lessened the impact of the raids. In 888 the energetic Odo became the first king of Francia who was neither Merovingian not Carolingian, and the Vikings suffered a number of defeats. They moved back to England, but discovered that in the mean time King Alfred had learnt much from his Frankish neighbours. He too had built up a series of forts, or burhs, and had equipped himself with an effective navy. In 896 the Scandinavian army split up, part going to Northumbria and East Anglia, and part south again to the lower Seine. It was not until 911 that the Frankish king, Charles the Simple, legitimized the authority of these Vikings by granting the area around Rouen to the Northman Rollo, thus creating what became the duchy of Normandy. The period of Viking expansion had ended and, in some areas, the 'reconquest' began: in Flanders, in central England under Alfred's son Athelstan, and even in Ireland, where in 902 an alliance of Irish kings temporarily expelled the Dublin Vikings.
The effects of these Viking raids on northern Europe are very difficult for the historian to assess. For a long time the negative aspects were paramount; historians influenced by the image of bloodthirsty pirates found in contemporary sources stressed the destruction of monasteries and the political confusion, and blamed the Vikings for the destruction of the Carolingian Empire and of the traditional and relatively peaceful ways of Old Ireland. More recently other historians, following Professor P. H. Sawyer in particular, noted the small-scale nature of Viking raiding and settlement. They pointed out that monasticism was on the wane in England before the Vikings; that the Carolingian Empire collapsed for internal structural reasons; that the Vikings did not bring an end to the immunity of the Irish Church from secular violence, for Irish monasteries had for decades been the victims of attacks by Irish kings, and indeed by the abbots of other Irish monasteries. Archaeologists, impressed by Scandinavian artistic and seafaring achievements, began emphasizing the positive contribution of the Vikings as craftsmen, sailors, merchants, and farmers. The Jorvik Viking Centre, which displays the results of the important excavation at Coppergate in York, exemplifies this approach. The simi-
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