Why did the accused Christchurch killer look to figures from the Middle Ages as his role models and emblazon the name “Charles Martel” on his firearm? Was he continuing a historic religious conflict between Christianity and Islam by celebrating this eighth-century duke who defeated an Arab army between Poitiers and Tours in France in 732 to stop the spread of Islam in Europe?

Yes, and no. Anti-Arab groups have invoked Martel as a source of inspiration for decades, seeing him as a defender of Christendom. French terrorists used Martel’s name in the 1970s and 1980s when they attacked Algerian businesses. In 2014, it was Stephen K. Bannon who invoked the battle when he called upon the Catholic Church to take a stance to defend the “Judeo-Christian West” from terrorists.

But Martel wouldn’t have considered himself a defender of Christendom. In fact, he simply fought to defend his own prerogatives and land and to defeat a rival. Nonetheless, anti-Arab forces are indulging in a centuries-long tradition: fabricating the tale of Martel to suit their own political purposes.

In reality, the earliest medieval account of Charles’s victory did not portray the battle as a clash of civilizations at all. At this time, kings were weak, and real power lay with territorial dukes who owned land, appointed judges and organized the strongest armies for defense. Charles, starting in what is now Belgium, rose to prominence through military victories against key rivals and invading pagan Saxons from the east. He consolidated power by rewarding lay and religious allies with land and honors. The battle of Tours, at the time, was just one more step on Charles’s path of conquest.

A history commissioned by Charles’s uncle claimed that the Arabs had been invited from Spain by another Christian duke, Eudo of Aquitaine, to help reclaim some land Charles had seized from him. This was no full-scale foreign invasion. But the Arab soldiers got out of control and burned some churches on their way north. Charles took advantage of this disarray, and claimed an easy victory. With the threat from Eudo and his allies finished, Charles proceeded to extend his control over the rest of what is now France with further military action.

But though Charles won many battles, few people celebrated him as a hero. Ecclesiastical writers saw not someone who had defended them, but an immoral opportunist who had abused their lands to reward his followers. One writer said you could see the scorch marks in St. Denis where Charles had been dragged down to hell.

The narrative of Charles and the Battle of Tours was transformed in the 18th century with Edward Gibbon’s “Decline and Fall of the Roman Empire.” This was a seminal work of history, still widely read today, that lamented how Europeans had lost touch with the civilizations of Greece and Rome. And in that story, the battle truly became about warring cultures. ‘The nations of Asia, Africa and Europe advanced with equal ardour to an encounter which would change the history of the world,’ wrote Gibbon with exciting and dramatic prose. He didn’t have new sources, but rather a new agenda. He concluded that if Charles had lost, Europe would quickly have been overrun by Arab invaders. He did not pause to consider more modest outcomes or the uncertain size of the armies involved.

The French were not convinced by Gibbon’s narrative, however. Jules Michelet, the 19th-century father of post-revolutionary French historical writing, considered the battle little more than a disorganized raid. The early French, he reckoned, had much more to fear from “Germanic invasion.” And Charles represented exactly such an invasion, coming as he did from land to the west of the Rhine. Franco-German conflict in Michelet’s own time, particularly during the Napoleonic wars, made the Germans more of an enemy than the Arabs.

By the 20th century, the Belgian historian Henri Pirenne came to similar conclusions in his famous book “Mohammed and Charlemagne,” published posthumously in 1937. He wrote to play down the importance of Germanic culture in Europe’s history after his own experiences in German prison camps during World War I. The end of the ancient world, and the beginning of the medieval, really began for him with the seventh-century Arab conquests of the Mediterranean. But even in that context, he believed Tours to be of no real importance.

Gibbon, Michelet and Pirenne did not come to different interpretations of Charles Martel and the Battle of Tours because any one of them had better or more sources than the other. Rather, they were trying to fit the story into larger narratives about crudely defined world civilizations or nascent nation states. Those stories brought with them different ideas about what Europe was and what it was not — defined by nations, ethnicities and cultures, more than by religion.

In reality, Charles did not see his standoff with Arab armies as a battle of civilizations. Arab expansion and the spread of Islam was so new in 732 that most people had little sense of how such things fit into a world otherwise framed by the Roman Empire and Christendom. Charles fought, as far as we can tell, simply to defend his own interests.

In claiming the legacy of Charles, the Christchurch killer is invoking a historical legacy that abuses history to justify violence. This is not a simple historical illiteracy — this is how Tours appears in many books and websites. What we need to understand and counter is how often historical moments such as Tours have gained their popular meaning through modern politics.