The struggles of Alfred with the ferocious Northmen have been detailed in more than one volume connected with the present.[276] During this period, there was a Danish monarchy in Northumbria, which, as we have already observed, had been probably founded by the sons of Ragnar Lodbrog. That monarchy subsisted in the reign of Edmund, the son of Alfred; and, it was in full vigour on the accession of Athelstane. So powerful, indeed, was Sigtrug, king of that province, that Athelstane, to insure his friendship, conferred on him the hand of his sister. The condition of this marriage was that Sigtrug should embrace Christianity, and become the vassal of Athelstane. In five years, however, the restless barbarian put away his wife, and relapsed into idolatry. To punish the insult, Athelstane invaded Northumbria; but Sigtrug died before his arrival; and the two sons of Sigtrug, Anlaf and Godfrey, fled,—the former into Ireland, the latter into Scotland; and Athelstane annexed Northumbria to his English crown.[277] [Sidenote: 924 to 934.] That Athelstane should so immediately raise the power of the Saxon kingdom, as not only to defeat the Danes and Northmen, but to subjugate a province which had always been hostile to it, shows what may be effected by the energies of a single mind. Not satisfied with expelling the enemy from Northumbria, he pursued them into Scotland, far north of the boundary which had hitherto arrested the progress of English victory: his fleets penetrated into Caithness, ravaging the coast as they proceeded. And he is believed, at this period, to have located a multitude of English colonists in the southern provinces of Scotland, and thus to have laid the foundation of the present lowland population. But Northumbria was too recent a conquest, and too dissimilar from the rest of the monarchy, to remain secure. The chiefs of Denmark and Norway, who had so long regarded England as a kind of inheritance, armed in greater numbers than before, to check the rising power of Athelstane. They were joined by all the noted sea kings of the age; by many of the jarls or kings who had settlements in Ireland and Scotland; by the king of the Scots, and by several Welsh chiefs. Never, we are told, had so formidable an armament menaced England as that which, in 934, entered the Humber. It consisted of 615 ships, headed by Anlaf, whom Constantine of Scotland had induced to make the attempt. Anlaf, who, on his father’s death, had obtained for himself a principality in Ireland, had a reputation for skill and valour equalled by none of his countrymen. Of the two thanes whom Athelstane had placed over Northumbria, one was defeated and slain; the other, after the battle, fled to acquaint the English monarch with the defeat. He prepared for the contest with courage; and, to gain time until his forces were collected, entered into negotiations. When his army was completed, he hastened into the north,