The Kalmar Union had formed thanks to the complicated intermarriages of Scandinavian royalty. Margret I of Denmark married Haakon VI of Norway (son of Magnus IV of Sweden and Norway), meaning that their son Olav had direct claim to the crown of Denmark and Norway as well as a strong bid for Sweden. Olav's young death meant that the crown would be given to an elected regent, who nearly always was Danish. While many Swedes balked, soldiers and fear of growing German power kept them in line. In 1397, the union was made formal by the Treaty of Kalmar, which created what hoped would be eternal united strength for all Scandinavia under one crown.
Their armies met at Brunkenberg, just north of Stockholm. Sten planned a pincer movement with his lieutenants: Sten would sweep in from the west while Nils Sture attacked from the forest on the northeast and Knut Posse marched from the city itself. Christian marched into the trap and suddenly found himself surrounded.
In the midst of battle, a musket ball hurled toward Christian's face, and he moved slightly enough for it to graze his cheek. The terror of near-death gave way to a feeling of powerful courage, as if God had given him a sign to cast out the rebels. He rallied his troops and began a charge toward Klara monastery, where some of his men had been cut off from the rest of the army. The other Danish forces held while Christian routed Nils and regrouped with the lost regiments. They moved from the north toward Sten, flanking him and causing his loyal army of farmers and miners to break under Danish might. When word spread that Sten had been killed in battle, the movement crumbled, and Knut Posse's army surrendered after considering a desperate defense in Stockholm.
The Battle of Brunkeberg would prove to be a great emblem for the Kalmar Union. Christian spread propaganda about his victory and commissioned sculptor Bernt Notke to carve a statue of Michael the Archangel slaying demons that had rebelled against Heaven. Refocusing Swedish economic policy toward autocracy, he squelched the growing ideals of democracy and reaffirmed Denmark as the leader of the Scandinavians. Wielding the might of the Kalmar Union, the Danes would gradually conquer southward and come to hold the Baltic Sea as their own.
Denmark would further its sphere of influence with great victories in the Fifteen Years' War (1618 to 1633), bringing about the collapse of the Holy Roman Empire and the establishment of free states within the Germanies and much of the Protestant north under their political sway. France, Spain, and Austria would unite against the growing Protestant threat over the next century in a series of wars that would ultimately lead to the forced breakup of the Union. They would attempt a new, more covert Holy Roman Empire under the guise of diplomacy and pitting Swedish, Danish, and Norwegian princes and dukes against one another for the next century.
During his conquests of Europe, Napoleon would reestablish unity for each of the people groups, but keep them under separate, hand-chosen kings. Disunited, but finally at peace, the Scandinavians would prosper greatly as they caught up to latter parts of the Industrial Revolution.
In reality, King Christian I would be hit by the musket ball, causing him to lose several teeth and order his guard to retire from the battle. They attempted to retreat to Käpplingen Island, but the hastily-built bridge was destroyed by Sten's troops, causing havoc while the rest of the Danes were defeated. To commemorate the battle, before which Sten said he prayed to St. George, he would commission the statue of St. George and the Dragon for Storkyrkan Church. Sten was assured as viceroy of Sweden, beginning the downfall of the Kalmar Union and the prelude to rule by the Vasas, who would assume power after Sten's death in 1503. After more altercations with Danish invasion, the Swedes would finally rise to dominate northern Europe in the 1600s.