Charlemagne was one of history’s most ruthless and ambitious warriors – King of the Franks, then King of the Lombards, conqueror of the Saxons, leading to the Pope crowning him Roman Emperor. But plenty of blood was spilled along the way. So how did Charlemagne manage to unite much of Europe? Why did the Pope crown him emperor? How did his legacy inspire Adolf Hitler? History Hit’s Rob Weinberg asks the big questions about this hugely influential figure to Dr. Sinead O’Sullivan of Queens University Belfast.