The Vikings: Why do the seafaring warriors still intrigue us?

Boyd Tonkin enjoys the latest blockbusting exhibition at the British Museum

Figures of berserkers made from walrus ivory (The Trustees of the British Museum)

Even in late February, well past the darkest days of winter, the sun rises slowly in Oslo. So when, before opening time, I enter the vast cruciform cathedral of the Viking Ship Museum on the Bygdoy peninsula, I find an eerie half-light inside. Jan Bill, the museum's curator and Oslo University's professor of Viking Age archaeology, searches for the right switches on a control panel. In the meantime, a magnificent, terrifying curved prow looms up out of the semi-darkness. Imagine, 1,000 or 1,200 years ago, dwelling not just along any coast between Greenland and the Black Sea but deep inland on a navigable river: Thames, Trent, Ouse, Shannon, Loire, Seine, Rhine, Dnieper or Guadalquivir (the Vikings raided Muslim-ruled Seville AD844). Suddenly, you awaken to witness scores of these great war-beasts, bristling with men and arms (94 ships attacked London in 994, in a joint Danish-Norwegian raid under Sweyn Forkbeard and Olaf Tryggvason). However nuanced the modern debates over Viking trade, art and statecraft, stand in front of these exquisitely carved vessels and one message booms down the centuries. This was shock and awe.

Lights on, and we contemplate the sleek grandeur of the Oseberg and Gokstad burial ships – the most complete of all survivals from that age. "This is the highlight of the Viking era," Jan Bill says. "And what's fantastic is that it's true." Excavated in 1904 from a mound on the west side of the Oslofjord, the Oseberg ship had 95 per cent of her original timbers intact. She was built circa 820, buried around 834 and miraculously preserved thanks to collapsed layers of clay. Found nearby in 1880, the high-sided, less flamboyant Gokstad vessel – built in the 890s, and at 23.25m slightly longer than the Oseberg ship – probably travelled farther on the open seas.

Carrying their prestige into the afterlife mattered to both ships' owners. The two women buried at Oseberg (one in her fifties, one in her eighties; perhaps a queen and her elderly servant) took with them as grave-goods finely carved sledges, a wagon, tapestries and even a bucket of Irish origin with an enigmatic "Buddha" carved on its rim. "We have all these artefacts that were usually not present," Jan Bill comments. "It really was an extraordinarily rich burial." The sledges, every strut and board a riot of foliage or animal figures, are stunning. Bill explains that "each of them represented a year of work for a skilled woodcarver. It was important for this burial to be very, very spectacular." At Gokstad, the fallen warrior (with battle wounds on his leg bones) even had a status-symbol peacock interred with him.

After a grave robbery around 975 – modern dendrochronology can date the spades used – the Oseberg mound lost its jewellery. Bill argues that, in keeping with the Viking obsession with prestige, simple theft wasn't the main motive. Rather, the pillage took place to show that a new dynasty – perhaps linked to Harald Bluetooth of Denmark – had taken charge in southern Norway. "This was probably a political act. The graves were not so much robbed as defaced and destroyed to show that this ruling power wasn't in power any more."

Bluetooth, a fearsome maritime networker who brought Christianity to Denmark, found himself commemorated in a different fashion a millennium later when he gave his name to a wireless technology. We can't seem to leave those Vikings alone. Hence the buzz of anticipation that has heralded the British Museum exhibition Vikings: Life and Legend. This is the museum's first major show since 1980 devoted to the raiders and traders who not only shaped the history of Scandinavia and the British Isles but left their mark from Newfoundland (where 1960s excavations at L'Anse aux Meadows confirmed the saga tales of voyages to "Vinland") to present-day Istanbul, where bored Nordic guards in the service of the Byzantine emperors scratched runic graffiti in the church of Hagia Sophia. For good or ill, this is living history. Which other culture of a thousand years ago could prompt angry op-ed pieces warning against "politically correct" reinterpretations that downplay the rape-and-pillage aspects to praise the sophistication of Viking culture?

For people in these islands, the Viking Age began with a 9/11 moment: the electrifying, out-of-the blue raid on the abbey of Lindisfarne in 793. Today, in the church near the ruined abbey, you can read a formal apology for the bloodshed – offered by a Norwegian bishop in 1993, 1,200 years later. Clearly, those longships still sail across our dreams. Recent findings argue for a high degree of interaction between (for instance) seafaring Scandinavians and land-bound Anglo-Saxons, rather than the atavistic enmity of Victorian myth. All the same, from dialect to DNA, the "Danelaw" territories ceded by panicky early English kings in the late ninth century still appear to mark a sharp cultural divide. Why is Essex not the same place as Sussex, and Yorkshire another world from Hampshire? Blame, or bless, those ubiquitous Norsemen.

At the British Museum, pride of place goes to the warship known as Roskilde 6: a giant military transport built around 1020. At 37m long and with 80 oars, the longest Viking vessel ever found was located in a fjord – already known for its many sunken ships – on the Danish island of Zealand in 1997. The huge ship may conceivably have belonged to Cnut the Great, who after 1014 united England, Denmark and Norway into a brief North Sea empire that marked the transition from provincial warlordism into national – and international – Christian kingship. Only 20 per cent of the massive warship's timbers survive. But an elegant steel cradle – carefully assembled after the British Museum welcomed this ultimate flat-pack delivery from the National Museum of Denmark – gives a fine impression of the whole.

I toured the British Museum show – the first to make use of the generous spaces of the Sainsbury Exhibitions Gallery – with curator Gareth Williams. Around the great ship, hoards of treasure, dug up all the way from Russia to Iceland, vie for attention with weaponry, jewellery, finery, household implements and the coins – many forged in the Islamic world – that prove just how far the Vikings travelled. Since the 1970s, Williams argues, the "biggest change" in our knowledge "is that now we have much greater appreciation of the scale of the Viking world". So dump those ideas of identikit shaggy blonds. "We don't see the Vikings as a single ethnic group. We see them as a culturally diverse group of people within Scandinavia who became even more diverse as they moved outwards." To Williams, "Viking is a job description. It's not an ethnic label."

But how much of that job involved terroristic mayhem, raiding and ransacking (a good Norse word), and how much peaceable craftsmanship, boat-building and commerce? For Williams, much of the lousy rep the Vikings endured came about because they had mounted violent assaults on scribe-filled monasteries – a bit like choosing to attack BBC Television Centre. In a rare reversal of the usual bias, "a lot of the history of the Vikings is written by the losers – or at least by those temporarily on the losing side".

Williams argues that we went through a fundamental transition in the 1960s, when a more cultivated – if not actually cuddly – image of the Norsemen took hold. However, "we went almost too far in the opposite direction. The truth is somewhere in between." In Olso, Jan Bill reckons that the high tide of revisionism came in the 1980s. "We viewed the Viking Age as perhaps more democratic. Today, there's more of a focus on power." The pendulum first swung from carnage to culture – but now state-making authority, from Iceland to Ukraine, takes centre stage again. Certainly, the artefacts tell of ostentation, hierarchy and intimidating display. "It's very much a bling culture," Williams says, chuckling. In pendants, bracelets, necklaces and brooches, chunky gold and fine-wrought silver flash from the cases.

Shackles and leg-irons add a sobering reminder of the slavery that faced the human haul from raids. Icelanders' DNA shows them to be Scandinavian in the male line; Irish in the female. The most complete account we have of a ship funeral – with the vessel burnt, not buried – comes from the Arab writer Ahmad ibn Fadlan, who travelled among the Vikings of the Volga in the 920s. In chilling detail, he recounts the mass, ritual rape of an intoxicated slave girl who was then stabbed and strangled as a sacrifice. Fantasy, propaganda? Alas, probably not.

The Oseberg ship at the Museum of Cultural History in Oslo (Eirik Irgens Johnsen)

The sheer range of Viking voyaging still astonishes. Williams has a favourite exhibit. The Vale of York hoard, one of several new discoveries in this fast-changing field, packs items from as far apart as Ireland and Samarkand into one plundered Frankish chalice. Its objects, buried around 927 just as the Wessex king Athelstan took over Viking York to create a unified "England" for the first time, embody three faiths: Christianity, Islam, and the worship of Thor, which endured so robustly (as in "Thursday"). "What is remarkable about it is that you have the whole of the Viking world within one cup."

From the monkish chroniclers who looked out to sea in dread, and the Icelandic saga-writers of the 13th century, up to today's historians and archaeologists, the Vikings have never lacked for fear or admiring attention. Yet so much about them remains undiscovered. "There's so much that we don't know – but so much that we do," Williams says. "We've got pieces of several different jigsaws in one box, and no one of the jigsaws is complete."

Jan Bill notes that, whether population pressure, ecological crisis, chieftains' ambition or political upheaval at home, the initial motive for all this overseas wandering is still a tantalising mystery. "There are so many ways you can explain it. We need an intensive, co-operative research effort to test the different hypotheses against each other."

Intriguingly, that effort must involve Russia, which took its name from a term for the Vikings (Rus) and yet has long denied its formative role. "There was an official line in the Soviet Union that the historiography of greater Russia was exclusively Slavic," Williams recalls. As the USSR broke up, this "anti-Normanism" lost its grip and a measure of glasnost applied to Viking studies, too. But many treasures still lie unexplored. "Once the political situation allows, I think that there is so much to be done in Russia," Jan Bill says.

Love them or loathe them, the Vikings generally feature among history's bragging victors – after all, Duke William of Normandy, who struck lucky at Hastings in 1066, was one of them. That makes the sporadic evidence of failure and calamity all the more haunting. In the British Museum, you will see evidence of a mass grave excavated at Weymouth in 2009. The skeletons, around 50, belonged to a company of Scandinavian warriors – thanks to isotope analysis, we can know that for sure – massacred together in the early 11th century. Perhaps a storm blew a boat on shore, where the forewarned men of Wessex lay in wait; perhaps a raid went catastrophically wrong.

"All of the injuries are consistent with execution rather than battle," Gareth Williams says. "'Death or glory' doesn't apply here. It looks as if they surrendered without a fight and were then killed." If the raiders had kept faith with the Norse gods, they might have hoped Valhalla would open its doors to them. Had some gone over to Christianity, thoughts of heaven would have brought comfort in their final moments. Others – as we know many Vikings did – might have hedged their bets on the afterlife, honouring old and new gods alike. Here all the splendour and swagger of the Oseberg and Gokstad ships has come to grief. For me, the bones of these forlorn seafarers brought to mind not any scholarly source, but a half-remembered poem: Rudyard Kipling's Harp Song of the Dane Women. "What is a woman that you forsake her/ And the hearth-fire and the home-acre/ To go with the old grey widow-maker?" µ

Vikings: Life and Legend, British Museum, London WC1, 6 March-22 June: britishmuseum.org; Viking Ship Museum, Bygdoy, Oslo, Norway: khm.uio.no