The first Battle for the Kingdom of Kattegat is an important military event of the Kattegat Civil War which saw the forces led by Ivar and King Harald of Vestfold-Rogaland fight against Queen Lagertha's loyalists and allies. The battle ended in a bitter and severe defeat for Ivar and Harald's forces, which took considerable casualties, although it didn't put an end to the civil war, for Harald and Ivar returned to Vestfold, where a few weeks later, they received important reinforcements and Frankish contingents sent by Duke Rollo of Normandy.
Negotiations took place early morning when the two armies met. Hvitserk was traded as a hostage for Halfdan. The leaders of the two armies met again the next day. Here all diplomacy failed and the armies had to result in battle.
Ivar the Boneless thought that his older half-brother Bjorn was perhaps trying an outflanking manoeuver, so King Harald allowed Ivar to take a third of the army to protect the ships. Hvitserk was ordered to move a handful of soldiers to the forest to try and outflank Lagertha's forces. King Harald will be commanding the main force of the army.
Lagertha and Bjorn decided to split the army to a great extent. Lagertha's allies will remain in the forest to act as outflank defense. While Lagertha will command the shield maidens with her grandson to flank their enemy. Bjorn was in command of the vanguard, this vanguard was split into 3 sections. Ubbe was in command of the front line, Halfdan was behind him and then Bjorn would lead the final assault.
The battle started when Bjorn gave the order "In the name of Odin, in the name of my father, attack!" King Harald order his army to advance at speed as well. Meanwhile, Hvitserk's group was ambushed in the forest by the Sami resulting in Hvitserk being forced to pull back very quickly. Ivar stopped on his way to reinforce his ships instead deciding to watch the battle.
The battle was shortly followed by shock charges in waves by both sides, but at the climax of the battle, Lagertha ordered the fatal blow that hit the army of King Harald in the rear, to make things worse for the forces of Harald, Bjorn ordered the final wave to hit the enemy. Ivar was called for immient help but Ivar was not able to provide aid and King Harald was forced to retreat after a humiliating defeat.
The battle was a strong victory for Lagertha's army. Due to the humiliating defeat at the hands of Lagertha's forces Ivar and Harald were to come up with a new plan in order to sway the next battle to come into their favor. Hvitserk ultimately reveals that Rollo promised if Hvitserk should ever need his help, he would just have to ask. Therefore the Frankish were called providing even stronger military support in the favor of Ivar and Harald's forces.