With these princes the supremacy of Mercia closed, for a great king had in the year 800 ascended the throne of Wessex. Ecgberht had lived as an exile in his youth at the court of Charlemagne, and there probably imbibed imperial notions. During his reign of thirty-six years he gradually brought under his power all the kingdoms of the English, whether Anglian or Saxon. In 823, at the great battle of Ellandune, he defeated the Mercians so completely that their subject kingdoms passed into his power. Four years later Mercia owned his overlordship, and Northumbria immediately after yielded without a struggle. These great kingdoms retained their own line of sovereigns as subordinate kings. Ecgberht continued the hereditary struggle against the British populations, with the West Welsh or Cornish, and the North Welsh or Welsh, and in each instance succeeded in establishing his supremacy over them. North of the Dee, however, his power over the British population did not spread. Thus the kingdom of the West Saxons absorbed all its rivals, and established a permanent superiority in England. [Sidenote: Period of Danish invasion. 790-1013.] Already, however, a new enemy, before which the rising kingdom was finally to succumb, had made its appearance; a year before his death, Ecgberht was called upon to defend his country from the Danes. This people, issuing from the Scandinavian kingdoms in the North of Europe, had begun to land in England, to harry the country, and to carry off their spoil. At first as robbers, then as settlers, and finally as conquerors, for two centuries they occupy English history. Their first appearance in this reign was at Charmouth in Dorsetshire. Subsequently, in junction with the British, they advanced westward from Cornwall. This led to the great battle of Hengestesdun, or Hengston, where the invaders were defeated (835). It seems not unnatural to trace the appearance of the Northern rovers in England to the state of the Continent. Driven from their own country by want of room, obliged to seek new settlements, they found themselves checked by the organized power of Charlemagne’s empire. They were thus compelled to find their new home in countries they had not yet visited. The reign closed with the capture of Chester, the capital of Gwynedd, the British kingdom of North Wales. [Sidenote: Æthelwulf. 836-857.]