Another reason the Vikings were successful was that in many places they attacked polities that were momentarily weak. They might not have won in Nantes if Charl

Another reason the Vikings were successful was that in many places they attacked polities that were momentarily weak. They might not have won in Nantes if Charles the Bald hadn't been busy fighting a civil war against other members of his family. Karl der Große's empire was falling apart, and like the Roman Empire had been vulnerable to the raid of Karl's ancestors, so was Karl's empire to the raids of the Vikings. Don't weep to the Franks, though: in the end, it was just a phase, and they were able to hit the Middle East during a period of weakness just a few centuries later.