Charlemagne was one of history\u2019s most ruthless and ambitious warriors \u2013 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\u2019s Rob Weinberg asks the big questions about this hugely influential figure to Dr. Sinead O\u2019Sullivan of Queens University Belfast.