In the month of November 885, an immense fleet of 700 Viking vessels - one of the largest naval assemblages of the entire warrior age - sailed up the River Seine, penetrating into the very heart of France. At its head were Sigfred and Orm, two Viking chieftains who had been raiding in Frankish lands throughout the decade. On and on they led their fleet, and they pillaged as they went, until, on the twenty-sixth day of that bleak month, they were 100 miles inland and before the walls of Paris. The city was then concentrated on the boat-shaped Ile de la Cite in the middle of the river and already crowned with a cathedral and controlled the Seine and waterways beyond. From this all-important island city, two fortified bridges arched over the river. The Vikings could proceed no further without taking them.

The ruler of Paris, Charles the Fat, a great-grandson of Charlemagne and nominal head of the dwindled Frankish empire, was preoccupied elsewhere with fractious cousins trying to secede from the empire. All that remained to guard the bridges were 200 Parisian knights and their men-at-arms under Count Odo, marquis of the province of Neustria, and Bishop Joscelin, the city’s ranking cleric.

Against this scanty defense, thousands upon thousands of ship-borne warriors hurled themselves into action. “Horrible spectacle!” exclaimed the monk Abbo, who witnessed the event from inside the precincts of the cathedral. In moments, the air was a blizzard of arrows. The stones of the fortress towers resounded with the clang of thousands of spears that were hurled against them. After the Vikings heaved flaming torches at the battlements, the whole city blazed with flames that, in Abbo’s words, painted the sky “the color of copper.”

Still, at day’s end, the ruined island city remained miraculously in the hands of its brave defenders. The Viking onslaught subsided - only to be renewed three days later. Then day after day, week after week, the Vikings pummeled Paris while Count Odo and Bishop Joscelin and their handful of stalwarts clung tenaciously to the walls of their city.

For all the ferocity of the attack, the Vikings did not succeed in taking Paris. But they did seize both banks of the river, and from there they held the city under siege for the better part of a year, simultaneously ravaging the French countryside for miles around. Not until late in 886 did Charles the Fat bring overdue assistance to the embattled Parisians, who by now were facing famine and pestilence. And then his action was that of a craven victim of blackmail. Instead of fighting off the Vikings, he granted them safe passage up the Seine, flouting the bravery of the Parisians - and, in addition, paid the warriors 700 pounds of silver to go and harass his rebellious subjects in Burgundy.

The long siege of Paris and its stunning aftermath exemplified how great Viking power and Viking ambitions had grown since the first few shiploads of warriors had descended howling upon England’s Lindisfarne monastery less than a century before. Those early summertime hit-and-run raids were the merest of larcenies compared with what the Norsemen learned to visit on the lands of northwestern Europe. As shrewd and pragmatic as they were violent, they soon saw the wasteful folly of returning home to Scandinavia, or even to the Shetland or Orkney Islands, after each raid. Instead, growing numbers of Vikings established quarters in easily defended islands in the mouths of the principal rivers that led inland from the sea, and they used them as bases for their murderous forays all year round.

Finding the land and the climate to their liking, these Vikings took to remaining as uninvited guests for longer and longer periods of time. And now in the last quarter of the ninth century, they swarmed out of their longships in ever-growing numbers, seeking not merely to loot but to conquer and carve out extensive territories to rule.

The mighty Viking invasions of France - and of England and Ireland as well - opened a new and fascinating chapter in the era of the Norsemen. The nature and history of the beset lands, the traditions and character of their peoples, and the strengths and weaknesses of the various Viking leaders made each of these three invasions markedly different from the others. And each produced a different - and sometimes surprising - result. In sum, they forever altered the course of medieval history.

Nowhere did the Vikings reach deeper, plunder with richer rewards, or settle more effectively than in the vast inchoate empire once ruled by Charlemagne. When Charlemagne died in 814, he left an enormous inheritance that reached from the Atlantic coast of France east to modern Hungary and from the North Sea south to the Mediterranean. All this went to his son Louis the Pious, so called for his ardent devotion to Christianity. In 823, Louis dispatched missionaries to Denmark in an early attempt to Christianize the pagan Vikings in their homeland. But he paid too little attention to the affairs of his earthly state - and to his own family. When he died, he left three quarrelsome sons - Charles the Bald, Louis the German, and Lothair, who for some reason seems to have escaped an epithet. These brothers went to war among themselves, which tore the empire asunder. Lothair retained the title of emperor and roughly the lands that are today Burgundy, Frisia, Lombardy, and Provence. Charles the Bald got the rest of what is now France while Louis the German got the lands roughly corresponding to modern Germany, which accounts for his name. And all three acquired packs of wolfish nobles as eager for plunder as the Vikings themselves. Naturally, the Vikings found this turbulent mass irresistible.

Typical of a number of brief alliances and rapid conquests made by the Norsemen was an incident that occurred in June of 842 along the River Loire, where an ambitious nobleman named Count Lambert was leading a rag-tag army in revolt against Charles the Bald. The count had been trying to capture Nantes - an old, Roman-walled city on the river - which would give him command of the province of Brittany. But his men could not breach the walls, and they had no way of attacking from the riverside - until the Vikings arrived in the area.

The Norsemen, in an expedition of sixty-seven longships, had sailed out into the Atlantic and down the west coast of France to the estuary of the Loire. There they stopped, confronted by a bewildering maze of shallow channels that meandered among brush-choked islands for a hundred miles upstream. They were apparently encamped, wondering what to do, when an emissary from Count Lambert arrived with a proposition. The count saw the Vikings as the answer to his prayers and offered to pilot them upstream to places of plunder in exchange for their help in capturing the city of Nantes. The Vikings, always keen to pounce upon any scheme that suited their purposes, readily agreed.

The date chosen for the combined attack was June 23 - and a shrewd option it was. June 23 was Saint John’s Eve, the shortest night of the year and one marked since prehistoric times in Europe by bonfires and fertility rites welcoming in the summer. For that reason, the people of Nantes would be too preoccupied with celebrating to notice what was happening on the river. The boats of the Vikings glided silently to a halt on the banks of the Loire at Nantes. There, with guttural roars now all too familiar along the coastlines of Europe, the warriors stormed into the merrymaking crowds, striking down people left and right and setting the tower afire.

Count Lambert, having wrested Nantes from Charles the Bald, then disappeared from history. Clearly, he gave the city no relief from the Vikings, who were to attack it in the future as they chose.

As for the immediate Vikings, after a few days they retired to the mouth of the Loire with all their booty. Then, instead of going home to Scandinavia, they settled on the large island of Noirmoutier just south of the Loire. From there, they scoured the countryside on both sides of the river, destroying towns, pirating merchant pack trains, and robbing farmers of their cattle and crops. “The number of ships increases, the endless flood of Vikings never ceases to grow bigger,” wrote the scholar Ermentarius about these years in the 840s. “Everywhere Christ’s people are the victims of massacre, burning, and plunder. The Vikings overrun all that lies before them, and none can withstand them. They seize Bordeaux, Perigueux, Limoges, Angouleme, Toulouse. Angers, Tours, and Orleans are made deserts. Ships past counting voyage up the Seine, and throughout the entire region evil grows strong.”

Charles the Fat’s ploy in 886 of paying the Vikings off in silver - such tribute came to be known as Danegeld, or “Danish money” - was neither the first nor the last futile attempt to encourage the Vikings to depart by making them rich. Between 845 and 926, French kings taxed their people unconscionably to make thirteen payments to the Vikings totaling more than 43,000 pounds of silver and 685 pounds of gold. And still the plunderers came back. So frequent were their visits that little was left of cities like Nantes, Orleans, and Rouen, which, from their locations on the Seine and the Loire, had served as marketplaces for the hinterland. The noblemen either fell in battle or fled from the marauders. The monks all deserted from their abbeys, and magnificent monasteries, such as Jumieges, which had kept alive a flickering flame of culture after the barbarian victory over Rome, were now only roofless, windowless walls.

But sometime at the end of the ninth century or the beginning of the tenth, there arose a Viking leader of extraordinary prowess and sagacity who shaped an entirely new destiny for the Vikings. His name was Hrolf, and he must have been an extremely large man: He was nicknamed Gongu-Hrolf, Hrolf the Walker, because no horse could carry him. According to a plausible legend, he was a Norwegian, scion of a family that had fled from Norway to northern Scotland to seek their freedom and fortune there. From that land’s fog-shrouded coastline of cliffs and narrow, rock-bound inlets, Hrolf took part in many raids, going sometimes to the coast of England, other times to that of France. By the early part of the tenth century, he and his followers had overrun and occupied part of the old Roman province of Neustria on the Seine.

It was a place worth having - rich with orchards and lush meadows that must have looked like paradise to a man brought up in the grim North. And Hrolf was evidently interested in more than loot, for he stayed on.

After many years that are veiled in darkness, the light of history flashes on for a brief moment in the year 911. At that time, Hrolf, his name by now changed to Rollo, reached an agreement with the Frankish king. He was another Charles, grandson of Charles the Bald, who had fought his brothers for the empire and won the lion’s share of France. This Charles - a youth in whom the blood of Charlemagne ran so thin that his subjects derisively called him Charles the Simple - was induced to sign a formal treaty with Rollo at Saint Clair-sur-Epte on a small river running into the Seine between Paris and Rouen.

By the terms of the treaty, Charles formally agreed to cede to Rollo what the Viking had already more or less taken - the broad valley of the lower Seine, soon to be called Normandy after the Norsemen. With it went the title of Count of Rouen, a designation Rollo’s descendants would magnify into Duke of Normandy as they expanded their holdings to a broad swath on the northwest shoulder of France, about 175 miles by sixty and bounded by the principal market towns of Bayeux, Chartres, Evreux, and Saint Lo. In return, Rollo was to swear fealty to the king, to look to the defense of his own domain, and to be baptized a Christian and defend the faith of the realm.

It is not difficult to imagine the contrast when these two ill-matched leaders met - Rollo, the giant of a Viking sea lord, his towering frame jangling with golden arm rings and amulets stamped with the hammer of Thor; Charles, elegant in linen shirt and breeches and a cloak decorated in silk, his head perhaps buzzing with illusions of imperial grandeur but no doubt haunted by fears of rebellion.

Despite their differences, both men recognized that they had certain goals that were reconciled by the treaty. Charles the Simple had the not-so-simple task of holding down more than a dozen fractious nobles in his own realm and dealing with repeated raids from the Vikings as well; Rollo wanted land to rule. The treaty served them both. For Rollo, it made lawful his presence in Normandy; for Charles, it provided a buffer between his beleaguered kingdom and new Viking arrivals from the sea.

Rollo could be a cruel man. According to one tradition, when some peasants sought the right to hunt and fish in Rollo’s woods, lakes, and rivers, he dispatched his uncle, Count Rudolph, to cut off a hand and a foot of each of the would-be poachers. But he was also sharp-witted and practical. He let himself be baptized, and he lost no time in restoring the churches that he and his fellow Vikings had sacked. His newfound Christianity probably did not significantly affect his personal beliefs one way or another. It was later recounted that, on his deathbed, he asked to be buried in the cathedral of Rouen and ordered large sums of gold to be given to Christian churches. He also called for human sacrifices to be made to the pagan gods. Presumably, then, whether Saint Peter or Thor met him in the hereafter, he would be assured of a welcome.

The immediate benefit from his conversion was political. He won the churchmen, who alone could read and write, over to his side. By showing favor to the Church, he got religious scholars and scribes to work for his interests, which were nothing less than the establishment of a workable state.

Settling himself at Rouen overlooking the Seine, Rollo kept his bargain with Charles the Simple; there were no further Viking raids upriver into Charles’s realm. Though he handed out parcels of land to his followers, he kept power tightly centralized in his own hands - belying an old tale his Vikings loved to tell about their first entry into Normandy: how when an officer of Charles the Simple shouted across a stream at the advancing Viking band, asking the name of their leader. The cry came back, “We know no masters. All of us are equals.”

Power was firmly arranged in a pyramid, with Rollo unchallenged at the top. In times of emergency, he supplied Charles with men-at-arms, and Viking men-at-arms were vicious fighters. Each year at harvest time, those same men-at-arms supplied a percentage of the land’s yield to Rollo, just as they supplied military service at his bidding.

Normandy as founded by Rollo was to become in only a few generations the most powerful state that Europe had seen since the fall of Rome 500 years before and the model of the medieval fiefdom.

As Rollo and his fellow Vikings put down roots in Normandy, they inevitably loosened their ties with their Scandinavian homeland. The Old Norse language was quick to go. The first wave of invaders had come over with few if any women; when the men settled down, they took French wives and concubines. The children grew up speaking their mothers’ tongue. Only a generation later, when Rollo’s son Duke William Longsword wanted his own son to learn the ancestral language, no one in Rouen could teach it. He had to send the boy almost a hundred miles away to Bayeux, which had the most recent arrivals from Scandinavia and, therefore, some speakers of Old Norse.

Rollo sired an extraordinary family. He was succeeded through six generations by descendants who shared his qualities of sharp wit, practicality, leadership, and administrative skill. In 1066, it was a sixth-generation direct descendant of Rollo’s, Duke William of Normandy, who achieved the greatest feat of arms in many an age - the conquest of all England, a strongly Viking England, in one blow.

As in France, the Viking presence in England had evolved through an endless series of raids, incursions, and devastations into invasions on a grand scale. Under the weight of the Viking assault, the petty kingdoms of East Anglia, Mercia, and Northumbria collapsed one by one, their strength drained, their royal lineages extinguished. By 880, only one Anglo-Saxon kingdom survived, Wessex in the southwest. And even that might have succumbed had it not been for the firm hand and cool head of the young King Alfred, who ruled there. He was the only English monarch to receive the epithet “the Great,” and he deserved it.

Alfred dealt with the Vikings on two levels - one political, the other military. It was obvious that the Vikings had overrun the lands to the north and east, and Alfred was enough of a pragmatist to accept that fact and seek to make it work for him. He drew up a treaty, which he signed with the Danish leader Guthrum, acknowledging the Viking claim to the conquered lands. Alfred, as the sole remaining Anglo-Saxon monarch of any stature, was signifying his people’s intent to live in peace, if possible, with the invaders. And he hoped to encourage them to work the land instead of incessantly trying to destroy it - and him.

But Alfred also knew that treaties gain force and acceptance only from the strength that backs them up. And so he set out to make Wessex impregnable. First, he revamped the levy system for fighting men. “The King,” says the Anglo-Saxon Chronicle, “divided his levies into two sections, so that there was always half at home and half on active service.” Under the new arrangement, men could be on their farms with their families half the time - and hence were less inclined to desert.

Next he built a series of fortified enclosures into which the peasants could drive their cattle and take refuge when Viking invaders appeared. Soon the Vikings were appearing less frequently in Wessex, for on the banks of the River Lea Alfred placed two forts that impeded an invader’s passage down the river.

Finally, and most important, Alfred was the only ruler in all Europe to deal the Vikings a blow with their own mightiest weapon - the warship. Sometime in the 890s, he ordered the building of a fleet. Alfred’s ships were “almost twice as long” as the Viking ships, relates the Chronicle. “Some had sixty oars, some more.” They were designed by the King himself, not on the Danish model, but, says the Chronicle, “as it seemed to the king they might be most serviceable.”

The Chronicle calls them swifter than the Viking longships, which is unlikely. But they were higher and more difficult for the enemy to board, and, as vessels to defend the coast, they were also probably heavier and steadier, with flat, barge-like bottoms that drew even less water than the Viking ships. In any event, they seem to have been remarkably effective. In one 896 skirmish, noted the Chronicle, Alfred’s ships caught six Viking vessels stranded at low tide in a southern port. Alfred’s men overcame four of the ships and killed most of the crewmen. Two vessels managed to get away. But during the year, relates the Chronicle, twenty Viking vessels, “men and all, perished along the south coast.”

Before he died in 899, Alfred alone in England had managed to stalemate the Vikings in combat. But more noteworthy, perhaps, the treaty he had signed in 886 with the Danish leader Guthrum appears to have had some of the calming effect Alfred desired. Instead of regarding the lands to the north as alien territory, the Vikings began to think of them as their own, to settle them, to meld with the Anglo-Saxon inhabitants, and to enrich them with the culture of their native Denmark.

This Viking sector of England comprised about 25,000 square miles and was bounded in the south by a line running diagonally northwest from just beyond London to Chester on the Irish Sea and in the north by a line running from the mouth of the River Tees to the North Channel of the Irish Sea. So Danish did it become that it was known as the Danelaw since the laws and customs of Denmark applied there.

How many Danes crossed the North Sea to settle as farmers and traders in the Danelaw is a question much debated by scholars. Some think that they formed only a thin layer of military aristocrats, who ousted English landlords from their property but did not otherwise occupy the land in any numbers. Other scholars believe that there was a massive migration from Denmark throughout the ninth and tenth centuries. They have two good reasons for thinking so. The most convincing is the fact that instead of losing their language, as did the Vikings who began to speak French in Normandy, the Danes had a powerful influence on the English language: Linguistically, they led rather than followed the local culture.

There are hundreds of place names in England ending in the suffix “by,” from the Old Norse meaning farm or village: Derby, Grimsby, Whitby, and so on. Even more pervasive are the thousands of Norse-derived words in the everyday English vocabulary. The modern Danish philologist Otto Jespersen once noted “an Englishman cannot thrive or be ill or die without Scandinavian words; they are to the language what bread and eggs are to the daily fare.” The list goes on and on: take, call, window, husband, sky, anger, low, scant, loose, ugly, wrong, happy. In the opinion of numerous scholars, so many and such fundamental words could not have been brought in by an army; they had to have come on the tongues of Danish mothers and children - and, of course, farmers, merchants, and craftsmen.

In addition to their language, the Danes brought laws and the means for enforcing them. In Scandinavia, they had kept the laws by oral tradition; they committed them to writing. A code for the year 997 in the Danelaw provides for courts consisting of twelve leading men - called thanes - to take an oath on sacred relics that they would neither accuse the innocent nor shield the guilty. “Let the judgment stand on which the thanes are agreed,” says the code; “if they differ let that stand which eight of them have pronounced.” Here is the first assertion in English law of majority rule and the first provision for trial by jury.

Whether they came as an army or as a migration, the Vikings did not massacre or drive out the native population. The two peoples lived side by side and sooner or later began consorting together - although not without some blue-nosed English expressions of indignation. A contemporary chronicler, John of Wallingford, complained sourly that the Danes were always combing their hair, changing their underwear and taking baths on Saturday “in order to overcome the chastity of the English women and procure the daughters of noblemen as their mistresses.”

But while the Danes and the English may have learned to live together more or less in peace, the Danelaw did not become a truly stable and efficient state on the Norman model. The Danish settlers never managed to throw up a leader of Rollo’s stature who was equal to the task of unifying the country and enforcing their democratically conceived laws. Instead, the Danes consumed much of their energy in waging petty feuds among themselves or in beating off incursions from their ambitious Viking cousins in Norway and elsewhere. And as the years wore on, some Danish chieftains again cast covetous eyes on the south and resumed their raiding across the border from the Danelaw.

Well they might, for southern England was growing weak and vulnerable. Throughout the realm made safe by Alfred the Great a century before, the fabric of government was rapidly unraveling. In 978, one of the most worthless kings in all of English history acceded to the throne. He was Ethelred, aptly nicknamed “the Unready,” who inherited the crown at the unripe age of twelve and for the rest of his life was benighted with personal indecision and poor counselors. In that sorry state, as the tenth century drew to a close, all England - not only Ethelred’s realm, but also the partially materialized Danelaw - was to face a formidable threat from the Vikings across the North Sea.

In Scandinavia, two leaders of note were securing their own realms - the Norwegian Olaf Tryggvason, descended from Harald Fairhair and in his own right a formidable warrior who went into battle resplendent in a scarlet cloak, and the Dane Sweyn Forkbeard. Both now turned their might abroad - not as freebooters but as kings bent on conquest.

The first attacks of the new Viking wave came in 991, when Norway’s Olaf sailed to southern England with a fleet of ninety-three ships. In quick succession, Olaf’s warriors ravaged the ports of Folkestone and Sandwich. Next, they landed within thirty miles of London, near the town of Maldon, on an island with a causeway leading to the mainland. There, an English leader named Byrhtnoth valiantly attempted to halt the Vikings. But he and his men were overwhelmed - and the whole of southeastern England lay open to the invaders.

The unready Ethelred’s unwise response to this threat was to try to buy Olaf off with a payment of 10,000 pounds of silver coins, brooches, arm rings, torques, and ingots wrung from Ethelred’s unhappy subjects, together with food and drink for the lusty Viking army.

That expedient was the first of many that succeeded only in enraging Ethelred’s Anglo-Saxon subjects. This time, the payment brought them relief from the Viking harassment - but only for three years. In 994, the Norwegian Olaf was back, this time allied with the Danish Sweyn Forkbeard. The two kings, after collecting 16,000 pounds of silver, returned to Scandinavia - but not for long. Sweyn was soon to return and embark on a campaign that would take him the length and breadth of England and occupy him for more than a decade.

He began in the southeast corner of Wessex. For the year 999, the Chronicle recounts how “the host again came round into the Thames.” This time, at long last, Ethelred gathered his courage and attempted to fight the invaders. What is more, he chose to make a stand. “The King with his counselors,” relates the Chronicle, “decided to advance against them with both naval and land forces.” Unfortunately for the feckless Ethelred, nothing went right. Delay followed delay, and neither the ships nor the soldiers ever saw combat. “So in the end,” notes the Chronicle, “these preparations were a complete failure. They effected nothing except the oppression of the people and the waste of money.” The Chronicle for 999 ends on that unhappy note, without recording the tribute exacted by the Danes, but it must have been great.

In 1001, the Danes returned again. After another year’s harassment Ethelred yielded once more, this time paying Sweyn 24,000 pounds of silver. Then Ethelred spitefully gave orders for “all the Danish people who were in the land to be slain on Saint Brice’s Day,” November 13. Here was a mindless atrocity, for there was considerable commerce between the English and the Danes, and numbers of Danes had settled peacefully in the south. How many were rounded up and butchered is not known. But the mass murders infuriated the Danish King Sweyn and for more reasons than one. Among those killed was his sister Gunnhild.

Sweyn had the means to retaliate, for he had been assembling a powerful force. Four military camps were scattered about the perimeter of Denmark, all of them on navigable waters leading to the sea. They were carefully planned compounds, each with a number of boat-shaped barracks built of wood for sixty to seventy-five men, presumably warship crews, and each camp with a stout defensive palisade around the perimeter. All told, the camps could quarter at least 4,000 warriors at a time. It was from these camps that Sweyn now launched a series of attacks on England with which the misbegotten Ethelred was quite unable to cope.

Though the English king mustered a warship from every 300 hides of his realm (a hide was a geographical unit representing about 120 arable acres), he could not control his fleet. In 1009, in a battle off Sandwich, the Vikings burned eighty of his vessels. Another twenty defected to the enemy, and Ethelred, said the Chronicle simply, “went home” - meaning that he deserted his forces and fled to his nearest redoubt.

The Danes anchored their ships in Sandwich on August 1 of that year, went ashore, and looted Ethelred’s kingdom far and wide, collecting 36,000 pounds of silver. By the following summer, the Danes were everywhere. “When the enemy was in the east, then our levies were mustering in the west, and when they were in the south, then our levies were in the north,” says the 1010 Chronicle ruefully. “In the end, there was no leader who was willing to raise levies, but each fled as quickly as he could.”

That same year, Norwegian Vikings, under yet another Olaf, this one surnamed Haraldsson, sailed up the Thames and tore down London Bridge with grappling hooks, inspiring the rhyme that is sung in nurseries to this day. A year later, in the autumn of 1011, the Danish Vikings of King Sweyn reached Canterbury and seized, among other prisoners, the elderly archbishop. They pelted him with stones and the severed heads of cattle before crushing his skull with an axe.

Throughout this decade that had been so tumultuous for the south of England, the Danelaw had been exempt from Sweyn’s attacks. But in the summer of 1013, he drew it into the fray. Advancing to York and Northumbria, he secured allies from among the Danish chieftains there, and then turned south to deliver a final crushing assault. In quick succession, Oxford, Winchester, Bath, and London fell. Ethelred fled for his life to Normandy, and Sweyn installed himself as king of all England.

Only five weeks later, the conquering Sweyn was dead at the age of fifty-five, whether of sickness or of an accident the records do not say. In Denmark, he left an heir - his son Cnut - who, though only eighteen years old, was equal to the task of carrying on where his father had left off.

In 1015, Cnut sailed from Scandinavia with 200 ships to claim his father’s legacy. He first crushed the straggling remains of Ethelred’s army and then routed another force raised by Ethelred’s son Edmund. Cnut next levied the highest single Danegeld in history - 82,000 pounds of silver from throughout the realm, of which 10,000 came from London alone. Then, instead of making off with the loot, he used it to pay off his troops and demobilize much of his army.

Some of the Vikings went home to Scandinavia, but many others settled down in the new realm they had conquered - chief among them Cnut, who ruled as king.

A saga says of Cnut that his nose, “which was long, narrow and slightly bent, somewhat marred his good looks.” And he had a full share of wild Viking blood in his veins; in a fit of rage over a chess game, according to legend, he ordered a minion to kill his faithful friend and brother-in-law, Earl Ulf. Nevertheless, he was in most respects a temperate, farseeing, realistic monarch. When his courtiers, bedazzled by his triumphs, told him he could make the tides stand still, he sat on his throne by the seaside, with the waves washing around him, to show them that he was human.

This Danish Viking gave England its first peace in a quarter century. Since Christianity was the religion of a majority of his subjects, he submitted to baptism. He restored monasteries and consecrated churches. And in a written code of law, the first to apply to all England, he proclaimed Christianity the faith of the land and required the populace to support the Church with silver and crops.

The secular portions of Cnut’s law spelled out, among other things, what may have been Western Europe’s first written inheritance tax. A certain percentage of the estate of an earl went on his death to the king; lower-ranking nobles paid proportionately less. Other taxes were raised annually to defend the realm and pay for professional soldiers and seamen; some 3,000 pounds, for example, was collected annually to pay the wages of the seamen on Cnut’s warships. These taxes were no doubt an annoyance, like taxes everywhere, but still they offered a merciful release from the extortionate Danegelds of yore.

When he died quietly in his bed in 1035 at the age of thirty-nine or forty, Cnut left an England united and prosperous, and content to be under Viking rule. It seemed that the Norsemen’s conquest was complete.

But Cnut’s sons proved not to be of their father’s stature. They fought constantly among themselves - like the Vikings of the past - and succeeded only in losing the crown of England to a son of Ethelred’s, Edward the Confessor. He, in turn, refusing out of excessive piety to sleep with his wife, produced no heirs at all. He thus guaranteed a scramble for succession, which led in 1066 to the Norman invasion that spelled the doom of the Viking era in England.

Scarcely sixty miles west of England, across a shallow sea, lay, another somewhat smaller island, fertile and well watered, and an early object of Viking attentions. This was Ireland. It was a country of contrasts, enormously wealthy in some things, abysmally poor in others, virtually leaderless yet indomitable, the easiest prey of all but, in the end, the victim that most frustrated the Norsemen, for the Vikings, despite all their force of arms, encountered qualities of canniness and resilience in the Irish that they found both befuddling and exhausting. They never did conquer Ireland in the sense that they subjugated England or carved a state for themselves in France. Indeed, in 1014, after the climactic Battle of Clontarf, the Irish could claim with some justice to have been the first to have thrust the Vikings back to the shores from whence they had come.

When the Vikings arrived on the island around 800, Ireland had the most intellectually advanced culture of the West. Its lush hills were crowned with uncounted monasteries; the bell towers of nearly 100 such institutions survived as late as the nineteenth, and no one knows how many more succumbed to the ravages of war and weather. These centers of study delved into all manner of subjects, from astronomy to theology, and contributed to the learning of England and the Continent. It was to Irish monks that Charlemagne turned when he founded a school at the Frankish court, and it was from Irish script and illumination that the exquisitely crafted Carolingian volumes of his descendants were derived.

But, for all the monks’ erudition, the great mass of the Irish were behind in affairs of this world. Economically, Ireland had no commerce more sophisticated than barter. Technologically, the Irish had no ships worthy of the name, only hide-covered fishing craft, and their weapons were inferior. The Viking invaders, says an old Irish poem, wrought havoc “because of the excellence of their polished, ample, treble, heavy, trusty, glittering corselets; their hard, strong, valiant swords; and their well-riveted long spears.”

Politically, the Irish had been living in virtual isolation since the beginning of history. They had not been visited by the Roman legions that had swept over Continental Europe and England in the first century B.C., and so they had not even the primordial vestiges of the legal codes and administrative practices that helped to forge the modus vi vendi between Vikings and natives in England and France.

Nor had they any experience in putting aside petty quarrels long enough to sustain a common cause against a common danger. Their only hierarchy was a kaleidoscopic collection of rival petty kings, whose ancient jealousies and quick tempers kept them at odds with one another and with the nominal high king who reigned at Tara, about twenty miles from the eastern coast. “Alas,” mourned one early chronicler, “it is pitiful for the Irish to continue the evil habit of fighting amongst themselves and that they do not rise together against the Norwegians.”

Throughout the seven sparsely settled provinces of Ireland - Ailech, Connaught, Leinster, Meath, Munster, Oriel, and Ulaidh - the only enemies the Irish had ever known were their neighbors, and the only strategies they employed in combat were expedients of the moment, frequently based on cunning and trickery. It was in that spirit that the Irish met the first serious Viking incursions in the 830s. And wondrous to say, that spirit of guile had its effects.

The first Viking invader of record was a Norwegian prince named Thorgils, who arrived with a fleet of 120 ships carrying 10,000 warriors. He quickly seized Armagh - the ecclesiastical polestar of Ireland and the wealthiest monastery of all. He drove out the abbot, installed himself as pagan high priest, and threw up a chain of earthworks running clear to the western province of Connaught more than 100 miles away, signaling his occupation of the northern quarter of the island.

It might have seemed as though the conquest of the entire land was scarcely a battle or two away. The Irish had no Charles the Simple to bargain with the Vikings for fealty in return for a duchy, no Alfred the Great to contain the invaders behind a well-guarded border. But then, according to legend, a curious thing happened to Thorgils, something he was powerless to defend against for all his thousands of retainers. The crafty King Maelsechlainn of Meath, sent out his daughter with fifteen warriors disguised as maidens, lured Thorgils and fifteen Viking captains to a lakeside tryst, and drowned the lot.

However it happened, it seems certain that Thorgils met his demise. Though his death left the Vikings in Ireland without a leader, they were not without a foothold. His troops had anchored their ships in estuaries all around the Irish coast and erected wooden forts there to secure themselves. Those little forts eventually expanded up the hillsides overlooking the coasts. They were the embryos of the cities of Cork, Dublin, Limerick, Waterford, and Wexford. And for the next three centuries, these cities were to be the focus of a drama that would pit not only the Vikings against the Irish, but Vikings against Vikings, and, strange to behold, Vikings and Irish against other Vikings and Irish.

Indeed, the first sizable invasion fleet to follow Thorgils’ came not, as might have been expected, from fellow Norwegians bent on avenging themselves against the Irish but from rival Danish Vikings who smelled a good source of plunder in their cousins’ newly established enclaves. In 849, these piratical Danes swept over the horizon in a fleet of 140 ships and fell upon the Norwegian builders of Dublin. For three years, the contending Vikings waged a tug of war over the city. And the opportunistic Irish took a hand, assisting the Danes from time to time in the prayerful hope that the newcomers would oust the detested Norwegians.

But it was an alliance to make an Irishman shudder. In the aftermath of a massive battle that lasted three days and three nights in 852, during which the Danes annihilated the Norwegians, messengers sent by King Maelsechlainn - he of the seductive daughter - came to the Danes’ encampment to offer congratulations on the splendid victory. To their horror, the emissaries found the Danes, with perfect Viking sangfroid, cooking their food in cauldrons placed on heaps of Norwegian dead. Sparing no gory detail, an Irish chronicle describes the scene, “with spits stuck in among the corpses and the fires burning them so that their bellies burst, revealing the welter of meat and pork eaten the night before.”

But the Danes seem to have redeemed themselves somewhat for that barbaric performance by handing over to the Irish a chest of gold and silver coins for Saint Patrick’s shrine at Armagh - a deed suggesting to the chronicler that “the Danes had at least a kind of piety.”

To the great pleasure of the Irish, it seemed as if the fratricidal Viking struggle might go on and on when a fresh contingent of Norwegians arrived the next year, this time under a prince known as Olaf the White. But before long the Irish had to look to their own devices. For Olaf soon routed the Danes - and then trained his lustful eye on bigger game. Gathering his forces, he launched a full-scale attack on the interior.

By now the Irish fully understood the ultimate Viking threat - absolute conquest - and they were also beginning to learn something about warfare. For the first time in the memory of Irishmen, the incumbent high king at Tara, Aed Findliath, managed to persuade his fellow kings to cease their interminable squabbling and rally behind him. A great army of Irish warriors was gathered, and they drove the Vikings out of the countryside, inflicting terrible casualties until the Norsemen reached safety within the walls of Dublin.

And then what transpired in this wildly convoluted saga of Irish and Viking? The victorious King Aed did not lay siege to Dublin in an effort to crush the Norwegians once and for all. Instead, he entered into negotiations with Olaf the White, at the end of which the king magnanimously offered Olaf the hand of no less an Irish maiden than his own daughter. How and why this stunning romantic alliance was brought about is not recorded. It may be that the king was shrewd enough to understand how fragile his coalition of Irish clans was and wished not to fight the Vikings again. Or perhaps he simply recognized the Vikings in their growing city centers as more or less permanent additions to the Irish scene, and he desired to benefit his people with Viking culture and trade.

Whatever he had in mind, the alliance had welcome effects on both counts. The raids on the Irish hinterland did diminish in the second half of the ninth century. But even more momentous, Dublin, Waterford, Wexford, Wicklow, and the rest were to bring the Irish their first exposure to urban life, with its amenities of flagstone streets, timbered walks, and fresh water brought in conduits of hollowed tree trunks. In the Viking cities, the Irish first became acquainted with the standardized weights and measures that were the basis of sophisticated trade. There they got their first taste of commerce based on coinage and gained their first experience with goods brought in Viking ships from every corner of the known world. It is a measure of the Viking separateness from - and simultaneously their contribution to - Irish life that, although the Scandinavian language was not to permeate Gaelic speech as it did English, some significant words entered the Irish vocabulary through the Vikings, among them margad for “market” and pingin for “penny.”

For a hundred years after the marriage of Olaf the White to a princess of Tara, Irish and Viking life continued its dizzying progression of will-o’-the-wisp alliances and hotheaded animosities. Not until the middle of the tenth century was any sustained attempt made to put the struggles to rest and forge a stable union that could be called a state. And when that did occur, it originated in an unexpected quarter - not with the Vikings but with the Irish and in the person of the son of a little-known king of Munster. The son was Brian Born, who made a life’s career of trying to tame Vikings and Irish alike - and he nearly succeeded.

Brian was born about 941 in the Munster countryside, the youngest of twelve brothers who grew up smarting under the sting of raids from the Vikings of Limerick, the major city in the area. And Brian devised deadly counterattacks, springing with his followers from caves and copses to ambush the Vikings on their way to and from the city. In time, the Vikings were driven from Limerick, and the provinces of Munster and neighboring Leinster were united under Brian. By 999, after some twenty-five battles fought over almost four decades, Brian had won sway over all the native Irish kings and had even captured Dublin, making a vassal of Sigtrygg Silkbeard, a one-eyed, half-Norwegian, half-Irish chieftain then ruling Dublin. Soon thereafter, Brian was styled Emperor of the Irish.

In that role, he brought a blessed end to the fighting. Ruling over a peaceable confederacy of kingdoms, he restored Ireland’s devastated churches and founded schools. He built causeways from the sea islands, bridges over the rivers, and highways over the land.

But the peace was too frail to last. After barely a decade, one of the Irish kings, Maelmordha of Leinster, reverted to type and plotted to overthrow Brian. In 1012, Maelmordha formed an alliance with Silkbeard, who had never truly accepted Brian’s suzerainty. The dampened hostilities flared up, and soon the country was in chaos. The climax came at the Battle of Clontarf - the epic battle of Ireland’s war-torn history.

Ireland’s social fabric was by now such a patchwork quilt that practically everyone had relatives on the adversaries’ side. Sigtrygg had Irish blood from his mother, a princess named Gormflaith, who had been married many times, once to Brian Boru, which made Brian one of Sigtrygg’s stepfathers. Sigtrygg, in turn, had married one of Brian’s daughters by another Irish wife, which made him a son-in-law of Brian’s. To top it off, the rebellious Maelmordha of Leinster was Gormflaith’s brother, which made him Brian’s brother-in-law and Sigtrygg’s uncle.

The political and geographical threads were as tangled as those of the family relationships. An Irish chronicle claimed that opposing Brian was an army “of all the foreigners of the Western world.” And, indeed, Sigtrygg had sent emissaries to Vikings everywhere, seeking allies and promising rewards of money, land, and adventure. He offered to two separate Viking Chieftains marriage to his mother (Brian’s ex-wife) and for a dowry the city of Dublin. Among those who answered the call were Brodir, ruler of the Isle of Man, a menacing fellow who tucked his long black hair into his belt, and Sigurd the Stout from the Orkneys. Each came with shiploads of warriors, bringing the forces of Sigtrygg and Maelmordha to 20,000. But rallying to Brian’s cause were 20,000 warriors representing all the clans of Ireland except those in the rebellious Leinster and a clan or two that remained neutral - plus one foreign Viking, a brother of Brodir’s named Ospak, who hated his sibling.

The two immense armies came together on Good Friday in April 1014. All day long they fought on a triangular plain at the confluence of the Tolka and the Liffey Rivers, just outside Dublin. When the day was over, 7,000 Leinster rebels and Viking allies were dead, and, although the Irish loyalists of Brian Boru lost some 4,000 men themselves, they claimed victory. But the seventy-three-year-old Brian was not on hand to celebrate. In the late afternoon, he had been struck in the head with an axe by Brodir, who, according to one account, caught the old man as he knelt at prayer in his tent in a nearby wood. Brian’s Irish followers took revenge worthy of Vikings by cutting open Brodir’s belly, tacking his entrails to a tree, and forcing him to march around the trunk until he died.

The Irish ever after celebrated the Battle of Clontarf as the supreme moment of national unity and liberation, the definitive triumph of the famed hero Brian Boru over the Leinster separatists and the Vikings. It is true that, after Clontarf, never again did a major Viking invasion fleet appear off the coast of Ireland. The Vikings apparently accepted the futility of trying to conquer the intractable Irish. But Viking influence was anything but dead in Ireland. The Vikings remained and learned to live in peace with the Irish. A number of them even continued to rule their city kingdoms and, as sagacious traders, brought profit to both themselves and the Irish. The Norwegian half-breed Sigtrygg Silkbeard, for one, survived the disaster of Clontarf and remained on his throne in Dublin all the remaining twenty years of his life.

His heirs, like those of other Viking chieftains, married Irish princesses until, over the years, they were assimilated into their adopted land and became as Irish as their mothers. As for their cities, Dublin, Waterford, Wexford, and the rest grew and prospered as a legacy of the Viking sojourn in Ireland. Rimming the southerly corner of the island, these cities gave the isolated Irish what they had never had before - a window onto England and the Continent and the world of trade beyond.