<P> Northumbria was the pre-eminent power c. 600--700, absorbing several weaker Anglo - Saxon and Brythonic kingdoms, while Mercia held a similar status c. 700--800 . Wessex would absorb all of the kingdoms in the south, both Anglo - Saxon and Briton . In Wales consolidation of power would not begin until the ninth century under the descendants of Merfyn Frych of Gwynedd, establishing a hierarchy that would last until the Norman invasion of Wales in 1081 . </P> <P> The first Viking raids on Britain began before 800, increasing in scope and destructiveness over time . In 865 a large, well - organized Danish Viking army (called the Great Heathen Army) attempted a conquest, breaking or diminishing Anglo - Saxon power everywhere but in Wessex . Under the leadership of Alfred the Great and his descendants, Wessex would at first survive, then coexist with, and eventually conquer the Danes . It would then establish the Kingdom of England and rule until the establishment of an Anglo - Danish kingdom under Cnut, and then again until the Norman Invasion of 1066 . </P> <P> Viking raids and invasion were no less dramatic for the north . Their defeat of the Picts in 839 led to a lasting Norse heritage in northernmost Scotland, and it led to the combination of the Picts and Gaels under the House of Alpin, which became the Kingdom of Alba, the predecessor of the Kingdom of Scotland . The Vikings combined with the Gaels of the Hebrides to become the Gall - Gaidel and establish the Kingdom of the Isles . </P> <P> The Merovingians established themselves in the power vacuum of the former Roman provinces in Gaul, and Clovis I converted to Christianity following his victory over the Alemanni at the Battle of Tolbiac (496), laying the foundation of the Frankish Empire, the dominant state of early medieval Western Christendom . The Frankish kingdom grew through a complex development of conquest, patronage, and alliance building . Due to salic custom, inheritance rights were absolute, and all land was divided equally among the sons of a dead land holder . This meant that, when the king granted a prince land in reward for service, that prince and all of his descendants had an irrevocable right to that land that no future king could undo . Likewise, those princes (and their sons) could sublet their land to their own vassals, who could in turn sublet the land to lower sub-vassals . This all had the effect of weakening the power of the king as his kingdom grew, since the result was that the land became controlled by not just by more princes and vassals, but by multiple layers of vassals . This also allowed his nobles to attempt to build their own power base, though given the strict salic tradition of hereditary kingship, few would ever consider overthrowing the king . </P>

The byzantine economy in the early middle ages was