The Battle on the Hill of the Ash is a military engagement that is part of the Mercian Civil War. It depicts the confrontation between the combined forces of the Kingdom of Wessex and the Vikings against the Kingdom of Mercia. The event takes place in Season 3 Episode 3, Warrior's Fate.
After the Wessex-Norse victory over King Brihtwulf, only Prince Burgred stands between Princess Kwenthrith and the throne of Mercia. After Prince Aethelwulf's scouts found where the Mercian army was camped, the Viking warriors under Ragnar prepared to climb the Hill of the Ash and go to battle.
Needing a scout to go on a probable suicide mission, Torstein volunteered. He had been injured in the previous battle, the Battle of Mercia, and had the have his left arm amputated. The Mercian troops, after seeing him, at first thought he was some kind of wizard, but they shot him with some arrows and he kneeled down. Then they approached him, and Torstein stabbed a soldier with a knife, and was killed right after that, dying in battle and earning his place in Valhalla.
Right after Torstein's death, the battle began. The Norse warriors charged at full force against the Mercian troops, killing most of them. Porunn, was severely wounded in the face, after a Mercian warrior punched and sliced her. Bjorn managed to save her, but Porunn would never fight again. Ragnar was injured as well, but it was a minor injury, after a javelin scratched his belly.
After defeating the Mercian forces on the hill, Prince Burgred had another army in a glade under the hill. Burgred's troops were surroundered by Wessex archers, under Aethelwulf's command. The archers started shooting at the Mercian soldiers, and Ragnar told Aethelwulf to spare Burgred. After most of Burgred's men were killed, the prince surrendered, ending the battle. He later joined his sister Kwenthrith, and told Ragnar he was advised by bad councilors and didn't wish to fight him that day, asking for forgiveness. With all Kwenthrith's opposers defeated, the Mercian Civil War ended.