Denmark had declared war on Sweden and sided with Napoleon. By turning against Denmark the former Marshal Bernadotte saved himself from the necessity of making an attack on the country of his birth. Lubeck surrendered, the Danes were defeated at Bornhœved, Kiel and Glucksburg were captured, and the whole of Holstein occupied. An armistice was agreed to. Denmark offered the diocese of Drontheim, but Prince Charles was resolved to expel Denmark from the Scandinavian Peninsula. January 14, 1814, peace was made at Kiel, Denmark ceding to Sweden the whole of Norway, except Iceland and Fero Islands, and receiving Swedish Pomerania and the island of Rugen in compensation.
Norway, united with Denmark ever since the days of Queen Margaret, in a relation of more or less neglected conditions, during which her original independence was lost, had of late not been satisfied to remain under Danish supremacy. The governing class of officeholders was to a great extent of Danish origin and tendencies, and the patriotism of the population at large dates from a later period. Among the more cultured classes the revolution in France and close relations with England had fostered a desire for political independence. The Danes made use of this fact in order to try to maintain the relation with Denmark in some way. The Danish crown prince, Christian Frederic, was in 1813 made governor-general of Norway. He was a man of some brilliant gifts, but without any great ability. By journeys in the country he acquired popularity and adherents. In February, 1814, a meeting was held at Eidsvold by men of prominence, who declared the prince regent. May 17th a constitution was adopted and Christian Frederic elected king of Norway. His courteous offer of extending his rule to Sweden was there met by derision. After a triumphal return to Stockholm, Prince Bernadotte gathered his forces and attacked Norway both by land and sea, the aged King Charles XIII. having command of the navy. An army of 20,000 Swedes entered Norway under command of Von Essen, who captured the fortifications at Svinesund. The navy took possession of the islands in the archipelago outside of Fredericstad, which town was captured, with the fortress Kongsten, 100 cannon and considerable stores of weapons and provisions. The Norwegian army of 30,000 men was located in various places with the central body of troops at Moss. The plan of Prince Charles was to enclose it from all sides. A smaller Swedish force of 3,000 men was repulsed by the Norwegians in two conflicts at Lier and Medskog, celebrated by the latter as important victories. In the meantime the Swedish army proceeded northward and the fleet penetrated to the bay of Christiania. The plan to enclose the Norwegian army at Moss was being carried into effect in order to finish the war by one single battle, when negotiations for peace were begun.