According to the saga, their father Ragnar was captured and killed by King Ælla in England after a foolhardy invasion attempt. Björn and his brothers, seeking revenge, attacked Ælla but were beaten back. As Ivar realised that the English king could not be defeated right away, he sought reconciliation. He only asked for as much land as he could cover with an ox's hide and swore never to wage war against Ælla. Then Ivar cut the ox's hide into such fine strands that he could envelop a large fortress (in an older saga it was York and according to a younger saga it was London) which he could take as his own. Ivar made himself popular in England and asked his brothers to attack again. During the battle Ivar sided with his brothers and so did many of the English chieftains with their people, in loyalty to Ivar. Ælla was taken captive and in revenge they carved the blood eagle on him.