But AElfred had hardly disbanded his troops when his enemies, roused by the arrival of fresh hordes eager for plunder, reappeared at Chippenham, and in the opening of 878 marched ravaging over the land.

The surprise of Wessex was complete, and for a month or two the general panic left no hope of resistance.

AElfred, with his small band of followers, could only throw himself into a fort raised hastily in the isle of Athelney among the marshes of the Parret, a position from which he could watch closely the movements of his foes.

But with the first burst of spring he called the thegns of Somerset to his standard, and still gathering troops as he moved marched through Wiltshire on the northmen.
He found their host at Edington, defeated it in a great battle, and after a siege of fourteen days forced them to surrender and to bind themselves by a solemn peace or "frith" at Wedmore in Somerset.

In form the Peace of Wedmore seemed a surrender of the bulk of Britain to its invaders.