The ablest king in England in the generation that followed Offa was Ecgbert of Wessex, who had long been an exile abroad, and served for thirteen years as one of the captains of Charles the Great. He beat Beornwulf of Mercia at Ellandune (A.D. 823), permanently annexed Kent, to whose crown he had a claim by descent, in 829 received the homage of all the other English kings, and was for the remainder of his life reckoned as Bretwalda. But it is wrong to call him, as some have done, the first monarch of all England. His power was no greater than that of Oswiu or Offa had been, and the supremacy might perhaps have tarried with Wessex no longer than it had tarried with Northumbria or Mercia if it had not chanced that the Danish raids were now beginning. For these invasions, paradoxical as it may seem, were the greatest efficient cause in the welding together of England. They seemed about to rend the land in twain, but they really cured the English of their desperate particularism, and drove all the tribes to take as their common rulers the one great line of native kings which survived the Danish storm, and maintained itself for four generations of desperate fighting against the invaders. On the continent the main effect of the viking invasions was to dash the empire of Charles the Great into fragments, and to aid in producing the numberless petty states of feudal Europe. In this island they did much to help the transformation of the mere Bretwaldaship of Ecgbert into the monarchy of all England.

Already ere Ecgbert ascended the throne of Kent the new enemy had made his first tentative appearance on the British shore. It was in the reign of Beorhtric, Ecgbert's predecessor, that the pirates of the famous three ships from Heretheland had appeared on the coast of Dorset, and slain the sheriff who would fain have known what manner of men they might be. A few years later another band appeared, rising unexpectedly from the sea to sack the famous Northumbrian monastery of Lindisfarne (793). After that their visits came fast and furious on the shore-line of every English kingdom, and by the end of Ecgbert's reign it was they, and not his former Welsh and Mercian enemies, who were the old monarch's main source of trouble. But he brought his Bretwaldaship to a good end by inflicting a crushing defeat on them at Hingston Down, hard by the Tamar, probably in 836, and died ere the year was out, leaving the ever-growing problem to his son Aethelwulf.

The cause of the sudden outpouring of the Scandinavian deluge upon the lands of Christendom at this particular date is one of the puzzles of history. So far as memory ran, the peoples beyond the North Sea had been seafaring races addicted to piracy. Even Tacitus mentions their fleets. Yet since the 5th century they had been restricting their operations to their own shores, and are barely heard of in the chronicles of their southern neighbours. It seems must probable that the actual cause of their sudden activity was the conquest of the Saxons by Charles the Great, and his subsequent advance into the peninsula of Denmark. The emperor seemed to be threatening the independence of the North, and in terror and resentment the Scandinavian peoples turned first to strike at the encroaching Frank, and soon after to assail the other Christian kingdoms which lay behind, or on the flank of the Empire. But their offensive action proved so successful and so profitable that, after a short time, the whole manhood of Denmark and Norway took to the pirate life.

Never since history first began to be recorded was there such a supreme example of the potentialities of sea-power. Civilized Europe had been caught at a moment when it was completely destitute of a war-navy; the Franks had never been maritime in their tastes, the English seemed to have forgotten their ancient seafaring habits. Though their ancestors had been pirates as fierce as the vikings of the 9th century, and though some of their later kings had led naval armaments Edwin had annexed for a moment Man and Anglesea, and Ecgfrith had cruelly ravaged part of Ireland yet by the year 800 they appear to have ceased to be a seafaring race. Perhaps the long predominance of Mercia, an essentially inland state, had something to do with the fact. At any rate England was as helpless as the Empire when first the Danish and Norwegian galleys began to cross the North Sea, and to beat down both sides of Britain seeking for prey.

The number of the invaders was not at first very great; their fleets were not national armaments gathered by great kings, but squadrons of a few vessels collected by some active and enterprising adventurer. Their original tactics were merely to land suddenly near some thriving seaport, or rich monastery, to sack it, and to take to the water again before the local militia could turn out in force against them. But such raids proved so profitable that the vikings soon began to take greater things in hand; they began to ally themselves in confederacies: two, six or a dozen sea-kings would join their forces for something more than a desultory raid. With fifty or a hundred ships they would fall upon some unhappy region, harry it for many miles inland, and offer battle to the landsfolk unless the latter came out in overpowering force. And as their crews were trained warriors chosen for their high spirit, contending with a raw militia fresh from the plough, they were generally successful. If the odds were too great they could always retire to their ships, put to sea, and resume their predatory operations on some other coast three hundred miles away. As long as their enemies were unprovided with a navy they were safe from pursuit and annihilation. The only chance against them was that, if caught too far from the base-fort where they had run their galleys ashore, they might find their communication with the sea cut off, and be forced to fight for their lives surrounded by an infuriated countryside. But in the earlier years of their struggles with Christendom the vikings seldom suffered a complete disaster; they were often beaten but seldom annihilated. Ere long they grew so bold that they would stay ashore for months, braving the forces of a whole kingdom, and sheltering themselves in great palisaded camps on peninsulas or islands when the enemy pressed them too hard. On well-guarded strongholds like Thanet or Sheppey in England, Noirmoutier at the Loire mouth, or the Isle of Walcheren, they defied the local magnates to evict them. Finally they took to wintering on the coast of England or the Empire, a preliminary to actual settlement and conquest. (See Viking.)

King Ecgbert died long ere the invaders had reached this stage of insolence. thelwulf, his weak and kindly son, would undoubtedly have lost the titular supremacy of Wessex over the other English kingdoms if there had been in Mercia or Northumbria a strong king with leisure to conquest. concentrate his thoughts on domestic wars. But the vikings were now showering such blows on the northern states that their unhappy monarchs could think of nothing but self defence. They slew Raedwulf king of Northumbria in 844, took London in 851, despite all the efforts of Burgred of Mercia, and forced that sovereign to make repeated appeals for help to Aethelwulf as his overlord. For though Wessex had its full share of Danish attacks it met them with a vigour that was not seen in the other realms. The defence was often, if not always, successful; and once at least (at Aclea in 851) Aethelwulf exterminated a whole Danish army with the greatest slaughter among the heathen host that had been heard of down to that day, as the Anglo-Saxon chronicler is careful to record. But though he might ward off blows from his own realm, he was helpless to aid Mercia or East Anglia, and still more the distant Northumbria.

It was not, however, till after Aethelwulf'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, Aethelbald, Aethelbert and Aethelred, 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 Aethelred, the third son of Aethelwulf, 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 Aethelred was mortally wounded.

Text extracted from the entry for ENGLISH HISTORY in the 1911 Encyclopedia Britannica, the text of which lies within the public domain.