Bjorn I of Denmark (The Kalmar Union)

Bjorn I, Bjorn Jærnside, was the eldest son of Harald IV Kesja and was King of Denmark for a decade in the mid 12th century.

Elected by a small group of Zealandic and Scanian nobility in the midst of a Wendish assault on Roskilde (in which his father had died) Bjorn did not enjoy a widespread support. Most of Jutland had actively defied his father and with reports of Bjorn assuming the kingship many of its lords now looked to his uncle Cnut Lavard for protection.

Civil war was inevitable between the two. Harald IV had already looked to remove Cnut and replace him with Bjorn in the early 1130s but revolt and increased Slavic raiding stopped the plans. Cnut for his part had embraced relations with the German emperors increasing his own lands and influence over the Western Wends. Both would-be-kings now raided each other's property but were evenly matched and both refused to back down. However the death of the Emperor Lothair III and a new struggle for the Imperial throne had weakened Cnut's position and Obodtrite raids slowly wore him down. At the Battle of Grasten in May 1139 his army was cut down by Bjorn's forces and he fled into exile in first Kiev, then Svealand.

Once Bjorn's domination of Denmark was secure he sought to extend its control of the sea and stop the debilitating raids that flowed from Pomerania. This took the form of a rudimentary national navy with which Danish troops could patrol the islands and Pomeranian coast, and even land men to visit coordinated raids on the Wends themselves.

Little of his domestic policy is known but it is assumed that he made considerable efforts to patch relations between Roskilde and the Jutland areas as his successors would find a more united kingdom. He made considerable donations to the church as well, possibly to atone for his activities in the civil war and much of Lund cathedral's lands were ceded to it by him.

Bjorn had married Katarina of Svealand in about 1135. They would have two daughters; Christina and Marianna. When Bjorn died in 1146 his nobles quickly elected his old rival Cnut Lavard as king, recalling him from exile. This they hoped would avoid another major war, after all Cnut was Bjorn's closest male relative at this point, and Cnut III of Viken had signalled a desire to claim the throne. Cnut V would use Bjorn's daughters to further his own diplomacy with Christina marrying of Eric VI of Svealand and Marianna marrying Cnut III of Anglia.