The Conquestof Kattegat was the invasion and subsequently conquest of Kattegat led by Lagertha in order to take back her home and the throne.
Many years ago, Lagertha used to live in Kattegat with her husband Ragnar, when Aslaug arrived pregnant of Ragnar. She then decided to leave Kattegat because she felt humiliated and insulted.
Before launching her attack, Lagertha made sure Ubbe and Sigurd travelled to Hedeby, where they got imprisoned.
Lagertha launched a surprise attack on Kattegat with her forces coming from both land and sea.
Lagertha began the battle with an advantage since she took the forces of Kattegat by surprise. Then, during the shield wall clash, Lagertha gave a signal to Torvi to command the archers hidden in rooftops and windows to fire, turning the battle to her side and eventually winning the battle.
Aslaug, realizing the battle was lost, walked to Lagertha, offering her the place as queen as long as she was allowed to go away alive. Lagertha allowed Aslaug to go free, but then shot her in the back with a bow, killing her.
When Ubbe and Sigurd were freed they traveled back to Kattegat, now under Lagertha's control. There they were told that their mother was killed. Ubbe, in anger, tried to attack Lagertha, but was stopped by the guards before reaching her. The two brothers were imprisoned again.