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A new study suggests the Battle of Clontarf (depicted here in an 1826 painting) was fought primarily between the Irish and Vikings, rather than between rival Irish factions.

Hugh Frazer/Wikimedia Commons

The Vikings were enemy No. 1 for Irish hero Brian Boru, social network study says

Every Irish schoolchild knows the story of the great Christian hero-king Brian Boru, who united his countrymen against the heathen Viking horde. Yet many modern scholars view his final battle—Clontarf in 1014—as mostly a civil war between Irish factions, with the Vikings playing only a small role. Now, a mathematical analysis of the war’s primary account suggests the traditional story may be closer to the truth: Although Ireland was indeed riven by a jumble of alliances, the authors say the conflict was primarily the Irish versus Vikings.

The research sheds light on the complicated cultural and political legacy of the Vikings in Ireland, says Søren Michael Sindbæk, a Viking archaeologist at Aarhus University in Denmark who wasn’t involved in the study. “The Vikings do not act as a monolithic group,” he says. “They enter into existing Irish power struggles which they catalyze in new ways.”

The primary account of the war between ancient Irish and Vikings, appropriately titled the Cogadh Gaedhel re Gallaibh, or The War of the Irish with the Foreigners, lists the travels, meetings, and battles of Irish kings and Viking warlords for nearly half a century. But the sprawling epic, collated from three different sources, is problematic. Historians aren’t sure exactly when it was written, its timeline makes no sense, and it’s a brilliant piece of propaganda that demonizes the Vikings. “It basically says Brian was a good guy and the Vikings were bad guys,” says the study’s lead author, Ralph Kenna, an Irish theoretical physicist and mathematician at Coventry University in the United Kingdom.

Some historians have argued that the tale was a way of strengthening the O’Brien dynasty’s claim on the throne, and that the real war was waged between clans in the province of Munster, led by Boru, and clans in the province of Leinster, supported by the Vikings. But there’s precious little archaeological evidence to support either side.

So Kenna turned to social network analysis—the kind Facebook uses to figure out who your friends are—to analyze the relationships between characters in the Cogadh. Sindbæk says that although this method is used increasingly in anthropology, applying it to characters in ancient texts is quite ingenious. Kenna and colleagues mapped out every interaction among the 315 characters mentioned in the Cogadh, and coded their more than 1100 interactions as either friendly or hostile. They then tallied the hostile interactions into a single scorecard: If the nastiness was Irish-on-Irish, the score went up. If it was Irish-on-Viking, the score went down. The final score was negative. That means it’s quite likely that the war really was a struggle primarily against the Vikings, Kenna’s team reports

Kenna admits the interpretation isn’t perfect, as it depends on the accuracy of the relationships described in the Cogadh. But even though the text is biased in its character descriptions, he doesn’t think its authors would have altered the actual alliances and conflicts. “There’s an art to propaganda,” Kenna says. “You can’t falsify too much or else people won’t accept it.”

Sindbæk agrees, adding that this kind of complex mathematical analysis might cut through the text’s overt spin to get at something real. “It enables us to unveil a different layer of the text, even one which might not have been … consciously constructed by the author.”