The house of Wessex continued to supply a race of hard-fighting and capable monarchs, who went on with Alfred's work. His son, Edward the Elder, and his three grandsons, Æthelstan, Edmund and Edred, devoted themselves for fifty-five years (A.D. 900-955) to the task of conquering the Danelagh, and ended by making England into a single unified kingdom, not by admitting the conquered to homage and tribute, in the old style of the 7th century, but by their complete absorption. The process was not so hard as might be thought; when once the Danes had settled down, had brought over wives from their native land or taken them from among their English vassals, had built themselves farmsteads and accumulated flocks and herds, they lost their old advantage in contending with the English. Their strength had been their mobility and their undisputed command of the sea. But now they had possessions of their own to defend, and could not raid at large in Wessex or Mercia without exposing their homes to similar molestation. Moreover, the fleet which Alfred had built, and which his successors kept up, disputed their mastery of the sea, and ended by achieving a clear superiority over them. Unity of plan and unity of command was also on the side of the English. The inhabitants of the three sections of the Danelagh were at best leagued in a many-headed confederacy. Their opponents were led by kings whose orders were punctually obeyed from Shrewsbury to Dover and from London to Exeter. It must also be remembered that in the greater part of the land which they possessed the Danes were but a small minority of the population. After their first fury was spent they no longer exterminated the conquered, but had been content to make the Mercians and Deirans their subjects, to take the best of the land, and exact tribute for the rest. Only in Lincolnshire, East Yorkshire and parts of Nottinghamshire and Leicestershire do they seem to have settled thickly and formed a preponderating element in the countryside. In the rest of the Midlands and in East Anglia they were only a governing oligarchy of scanty numbers. Everywhere there was an English lower class which welcomed the advent of the conquering kings of Wessex and the fall of the Danish jarls.