"OUR DEFEATS have never threatened our national survival," John Keegan writes of the English in The Face of Battle; but that is to suppose that history began around the time of Magna Carta. For nowhere --this century -- has national survival been more calamitously threatened than in England in 1066; and never was there a blacker divisiveness between conquerors and conquered than that between the English people and the Normans who seized their country, their throne, and their land. What happened to a society based on a hierarchy of protection and obligation, with the beginnings of a parliamentary system, when it was overrun by invaders from a militaristic autocracy is one of the catastrophes of this millennium, although many claim that in its eventual consequences -- a reshuffling of the European balance of power -- the Norman conquest was, in the words of the authors of 1066 and All That, "a Good Thing."

David Howarth, the author of a brilliantly imaginative new examination of the events of that fatal year, is not so sure it was. Like all who have argued about 1066 for centuries, he has just 20 accounts to go on, 12 of them written within living memory of the year, six others in the same century --most of them works of Norman propaganda. But he has seen things afresh, rereading the sources with skepticism, common sense, and a keen psychological insight. He is the author of incomparable accounts of Trafalgar and Waterloo, but those battles are as accessible as The Bulge; the men of Hastings are known mostly through monkish argument and the animated cartoon figures of the Bayeux tapestry. Out of these fragile remains, taking care not to read modern motives into medieval minds, Howarth resurrects a vivid world of men in crisis.

The English lived in isolated villages, from which paths led out through the forest to places beyond that most never saw -- the world of folklore where the son sets off to seek his fortune. Every man had his place, yet each had a voice in public meetings --moots -- held in village, hundred, and shire, with the witenagemot above all, advising the king and confirming his successor when he died. The church was obedient to Rome, but the Testament was in English, and civilized arts flourished. It was a peaceable world, with dim memories of the last Viking raids.

In January of 1066, after a languid reign of 24 years, Edward the Confessor died without an heir. Godwin, Earl of Essex, and later his son Harold had exercised the power behind the throne while the king hunted and prayed, and finally, on his deathbed -- in spite of vague promises made years ago to William, Duke of Normandy -- named Harold his heir, subject to the witan's approval. Except for royal birth, Harold answered every kingly requirement: he was a just man, handsome, courteous, good-natured, had governed well for years without enemies -- except for an aggrieved, deranged brother, Tostig. He was crowned with genuine popular consent.

In Normandy the news of the coronation enraged Duke William. Not only had Edward promised him England, he believed, but Harold himself had once been maneuvered into swearing to support William's claim. What William did not understand --and the Norman invasion was based on the misunderstanding -- was that succession to the English crown was not arranged by kings and their advisors, but, as a constitutional right, by the English people through their representatives at the witenagemot.

How should he have understood? Both English and Normans had come out of the north, but now England had a written code of law, the Normans none; England was unfortified, Normandy bristled with castles that were home to a class of armed ruffians bred in the chivalric tradition who galloped about looking for trouble and making it.

William, who ruled this turbulent society by edict and the force of an alarming personality, was not about to take Harold's coronation lying down. He sent messages saying so, and by April Harold had assembled an army on the south coast to repel invasion. It was in part professional, some 3000 house-carls who fought on foot with two-handed axes; and a citizen army, the fyrd, made up of landholders doing two months' military service a year, who fought with spears, clubs, and knives. Harold's ships, like his small horses, were only used to get soldiers from one place to another, not for fighting.

At Eastertime an ominous light blazed across the night sky -- Halley's comet; the English were unnerved. Then Tostig attempted a hapless mini-invasion, failed, and skulked off to Scotland. In Normandy, William presented an invasion scheme to his barons. It was irrational to the point of madness. Normans were not seamen like their ancestors, yet he proposed that unmaneuverable ships should carry thousands of soldiers and horses (big hunters) and arrive as an orderly fleet at a chosen site, ready to go ashore and do battle. Though they promised to build the ships, the barons were in no hurry to participate in this lunatic caper.

William looked for outside support, most successfully in the Vatican. Without a word to Harold, or hearing a word in his defense, the Pope backed up William's claim. The invasion would be another crusade: William offered his army loot, land, and now salvation.

Elsewhere yet another invasion was being mounted against England.The half-cocked Tostig had gone to the King of Norway, Harald Hardrada (meaning Tough Customer) to persuade him to grab the English crown. Vikings loved nothing better than battle; their conduct gave the word berserk its meaning, and Harald was a more ferocious warrior than most. He jumped at Tostig's invitation. (These vivid events come from the 12th-century Icelandic historian Snorri Sturlasson.)

By early August the newly built Norman fleet, some 350 dragon ships, lay in the mud waiting for a southwest wind; but for a month it blew from the north. On September 8, as the equinox approached, Harold's fyrd went home, having served long beyond its regular term. Summer was over, and with it the threat of invasion.

Unaware of his competition, Harald Hardrada had seized the north wind of August to blow him down upon the east coast of England, where burning and pillaging he went up-river toward York, the dragons' heads of his fleet glaring over the meadows. When this news reached London, Harold marched north with his house-carls, gathering volunteers along the way. On September 25, as Harald Hardrada and his men lounged near Stamford Bridge, an army appeared: "It looked like a sheet of ice when the weapons glittered," says Snorri. Harold had marched his men 250 miles in four days. A hand-to-hand battle lasted all day. Harald and Tostig were killed; Harold's victory was complete. But he was merciful: he took no hostages, forgave the survivors, and sent them home. Just then the north wind shifted to the south: during his victory fest Harold learned that William had landed on September 28th.

He moved up the coast toward Hastings. The Domesday Book tells what happened to the towns that lay in his path. Their taxable value in 1066 just before and after the invasion, then 20 years later, is listed. A few were unchanged, some halved, some "waste" --laid waste.

Harold had been an inspiring leader, but now something broke him. Back in London he had a message from William. "When Harold heard it," says one account, "he grew pale and for a long time remained as if he were dumb." Then he announced he would march to battle at once: "May the Lord now decide between William and me." No one knows what the dumfounding message was, but Howarth guesses that Harold first learned that the Pope had backed William, that he himself had been found guilty, even perhaps excommunicated. One of his brothers sensibly proposed to lead the battle while Harold rested and prepared to carry on a long campaign should it be lost. But Harold refused: he wanted one fateful encounter. The Battle of Hastings was fought on October 14.

Harold's was the last homogeneous army in history, some 8000 men without divisions or horses, jammed together on a ridge. William's men were fewer, but in three divisions, each with archers, foot soldiers, and mounted knights -- 3000 of them. And William had a potent psychological advantage: his papal banner and blessing.

The Normans charged, shouting, "God's help!"; the English, "Out! Out!" (pronounced oot ).

English battle axes cleaved into Norman horses; Norman arrows rained on English heads. The English army never moved as it beat back attacks, and Harold, instead of galloping among his men like William to cheer them on and give orders, stood still in the rear with his axe and sword. "As the waning wood falls to the stroke of the axe," a French account related, "so the forest of Englishmen was brought to nothing." Yet the sides were pretty evenly matched: the battle lasted until dusk and Harold's death. An arrow may have pierced his eye: certainly William and three knights hacked him to pieces after he was wounded and perhaps blind; he was beheaded, disemboweled, and castrated.

In the weeks following, William laid waste to the countryside around London as later he made hundreds of square miles a desert for generations to come. He was crowned on Christmas at Westminister. Two hundred thousand Normans and Frenchmen came to live among the English; 300,000 Englishmen were killed or starved to death. William taxed them unmercifully; he stole the treasures of their churches and monasteries, stole their land, almost all of it, and divided it among his henchmen: he humiliated, impoverished, imprisoned, blinded, and castrated their leaders; he oppressed the poor. Farmland was turned into hunting preserves, castles were built everywhere to protect the interlopers from their unwilling tenants and to provide dungeons in which Englishmen could be locked up at a whim. The moots were abolished, the law was abrogated, a lively, flexible social system was destroyed.

It is argued that there are no decisive battles, that individuals and chance don't count for much; but in this tragic history, where improbable runs of luck -- good for William, bad for Harold -- played so large a part in what happened, it is hard to resist the old-fashioned view, even to see, as the protagonists did, the hand of a jealous God at work.