King Harald's english campaign is a military event in season 5 of Vikings. King Harald of the kingdom of Vestfold-Rogaland decided to launch a massive raid on Wessex , in order to plunder and pillage it as well as to weaken its defences. The campaign was part of Harald's plan to overthrow King Ivar upon returning to Kattegat, alongside his ally Jarl Olavsonn . However, the campaign ended in failure as King Harald was severely beaten by the West Saxon army. During the battle of Marton , Harald may have lost up to half of his army, as well as his ally Jarl Olavsonn who was struck by two arrows.