The Battle of Repton is a military engagement that is part of the Great Heathen Army's First Invasion. It depicts the confrontation between the Great Heathen Army and the Kingdoms of Mercia and Wessex. The event takes place in Season 4 Episode 20, The Reckoning.
Upon learning of the total defeat of King Aelle's army in the Battle of York, and Aelle's death, Prince Aethelwulf gathers the armies of Wessex and Mercia and moves out to intercept the advancing Vikings in the city of Repton.
As the Saxons approach the Norse vanguard, the Norse retreat. The Saxons race after them, but become confused when the Vikings seemingly vanish into thin air. Meanwhile, Bjorn and a large contingent of archers are moving through the forest and are hidden from the Saxons' view. The Viking vanguard suddenly appears behind the Saxons. Aethelwulf orders his army to chase them as the Vikings retreat yet again. As the Saxon Army chases after the Vikings, Bjorn and his contingent of archers unleash a rain of arrows onto the unsuspecting Saxons from close range, killing dozens before the Saxons are able to form a defense with their shields. When they finally form a shield-wall, they begin advancing. Suddenly, the archer's arrows stop, leaving the Saxons confused once again.
Yet again, the Norse vanguard appears in the sight of the Saxons. Aethelwulf moves his army to engage them, but the Norse retreat, only to appear behind them yet again. Tired and frustrated, Aethelwulf refuses to be embarrassed and played by the Viking one more time. He orders his men to attack the beached Norse ships. However, Ivar had predicted that Aethelwulf would do this. As the Saxons march towards the Viking camp and their ships, they are forced to move through a tight valley. Suddenly, the Viking archers reappear to ambush them from both sides, killing hundreds of soldiers as they struggle to form up. Next, a massive Viking force led by Bjorn appears in front of the Saxons and forms a shield-wall blocking their path.
Realizing that he has walked right into the Vikings' trap, Aethelwulf decides that he has no other choice but to charge the Viking shield-wall and try to break through it. He orders the Saxon forces to charge. The two armies collide, all the while the Viking archers continue to exact severe casualties on the Saxons. Aethelwulf bravely strikes through the Viking ranks, but he is pushed off his horse and has to start fighting on foot in the muddy field that is filled with hundreds of bodies of his men. With the Saxon Army already severely depleted from the archers' ambush, and physically exhausted from chasing the Viking vanguard, the Vikings are able to make quick work of the Saxons. They also have the added benefits of fresh numbers and sheer ferocity. Aethelwulf is practically knocked unconscious. As he recovers, he sees the butchery of his men taking place all around him.
If possible, things get even worse for Aethelwulf and his soldiers when a horn signals the arrival of the Viking rearguard, which is under Ivar's command. The rearguard traps the Saxon Army from behind. The Saxons are now essentially contained by Vikings from all sides.
Realizing the fate of the battle is all but decided, Aethelwulf orders his remaining men to retreat. Aethelwulf and his soldiers escape to Winchester to begin evacuating the city. The Vikings cheer in victory upon this complete rout of the Saxon Army. Ragnar's sons join in the cheering, except for Bjorn, who rather clear-sightedly understands that the campaign to avenge their father is not finished because Aethelwulf and Ecbert still live.
The battle results in an overwhelming victory for the Vikings. They now have all the time and no further opponents to face on their way to rampage Winchester. Half of Prince Aethelwulf's army is dead and the remaining troops are scattered and frightened. Meanwhile, the Great Heathen Army suffered very few casualties. There is no longer any standing army left to resist the Norse invasion.