It was not till 876 that Alfred’s reorganisation of his realm was put to the test. In that year a great Viking host under the kings Guthrum, Oskytel, and Amund made a sudden dash into Wessex, appeared in Dorsetshire, and seized Wareham, where they stockaded themselves between the Frome and the Trent in one of their usual water-girt camps. Alfred was soon upon them with the whole levy of Wessex, and held them so tightly blockaded—he made no attempt to storm their works after the experience of Reading—that they asked for terms, gave hostages, swore their greatest oath, and promised to depart. But when the king was off his guard all that part of the host that was provided with horses made a sudden sally, slipped through the English lines, and rode day and night till they reached Exeter, which they took by surprise. There they again stockaded themselves, and lay entrenched for the winter of 876-877. The indefatigable king followed them, again drew lines round their camp, and beleaguered them till they were oppressed with famine. They were depending for their relief on a squadron which was to run down the Channel and join them at the mouth of the Exe; but Alfred sent his fleet, such as it was, to intercept the incoming pirates. There was an engagement somewhere off the south coast, from which the Danes retired without winning a victory, and immediately after a great storm cast their vessels on the cliffs of the Isle of Purbeck. A hundred and twenty galleys, with all their crews, are said to have perished near Swanage. Reduced to despair by this news, the Danes at Exeter asked for terms, and departed for Mercia before the summer was out. This campaign had been such a complete success for Alfred that the events of the next year are a perfect surprise to us—as indeed they were to the contemporary observer; “slay thirty thousand of these heathen in one day,” says Asser, “and on the next sixty thousand will appear.” In the first days of January 878 the main army of the Vikings, starting from Mercia, made a sudden and unexpected descent on Wiltshire, cutting the West-Saxon realm in twain. From a central camp at Chippenham they raided east and west into Hampshire on the one side and Somersetshire on the other. At the same time a separate pirate fleet which had spent its Yule in South Wales crossed the Bristol Channel and threw itself upon North Devon. It must have been the sudden and unexpected character of such an attack at mid-winter which for a moment seemed to have crushed Wessex. The king, who appears to have been in the west at the time, threw himself into the Isle of Athelney with a small band of his thegns and personal retainers, and there built his famous stockade in the marshes of the Parret. Elsewhere there was panic: many men of note fled over-seas to the Franks: large districts offered tribute and submission to the Danish king Guthrum.