It's quite historically inaccurate. It's based on the mythical Saga of Ragnar Lodbrok (who may or may not have been a real person) and peppered with artistic license, like Aethelstan, Ragnar's Anglo-Saxon slave-turned-brother monk, who just happens to have the name of the first English King who popped up a few decades after the seige of Paris, and how the events in the show seem to mirror real life events that occurred across a 200-year timeline. And their lack of any battle armor. But it's a fantastic show.
