It was not, however, till after Æthelwulf's death that the attack of the vikings developed its full strength. The fifteen years (856-871) that were covered by the reigns of his three short-lived sons, Æthelbald, Æthelbert and Æthelred, were the most miserable that England was to see. Assembling in greater and ever greater confederacies, the Danes fell upon the northern kingdoms, no longer merely to harry but to conquer and occupy them. A league of many sea-kings which called itself the "great army" slew the last two sovereigns of Northumbria and stormed York in 867. Some of the victors settled down there to lord it over the half-exterminated English population. The rest continued their advance southward. East Anglia was conquered in 870; its last king, Edmund, having been defeated and taken prisoner, the vikings shot him to death with arrows because he would not worship their gods. His realm was annexed and partly settled by the conquerors. The fate of Mercia was hardly better: its king, Burgred, by constant payment of tribute, bought off the invaders for a space, but the eastern half of his realm was reduced to a wilderness. Practically masters of all that lay north of Thames, the "great army" next moved against Wessex, the only quarter where a vigorous resistance was still maintained against them, though its capital, Winchester, had been sacked in 864. Under two kings named Halfdan and Bacsceg, and six earls, they seized Reading and began to harry Berkshire, Surrey and Hampshire. King Æthelred, the third son of Æthelwulf, came out against them, with his young brother Alfred and all the levies of Wessex. In the year 871 these two gallant kinsmen fought no less than six pitched battles against the invaders. Some were victories--notably the fight of Ashdown, where Alfred first won his name as a soldier--but the English failed to capture the fortified camps of the vikings at Reading, and were finally beaten at Marten ("Maeretun") near Bedwyn, where Æthelred was mortally wounded. Alfred the Great.