I invite posters to read Wikipedia's write-up of the battle of Edington. Many names used in Vikings appear in the write-up. There were several earlier battles in Wessex (Ashdown) and others over about a 7-9 year period. You'll see Alfred, Aethelred (preceded Alfred as King), Ivar, Ubbe, Halfdan Ragnarsson, and "Aethalstan". From other sites one finds that Ivar is ordering this war that is led by others (brothers and so on). One of Ivar's brother is killed and one is baptized as a Christian. There is more to find if you research the subject deeper.