As early as in 1812, prior to the Napoleonic invasion of Russia, the Swedish Crown Prince Charles John had entered into an agreement with Tsar Alexander I that Russia would support a Swedish attack on Norway in order to force Denmark-Norway to cede its northern part to Sweden. The Swedish attack against Norway was postponed, however, due to the fluid state of the conflict between Napoleon and the Sixth Coalition. The Swedish army and, incidentally, Bernadotte's skills as a general, were urgently needed against France in Central Europe. On 18 May 1813 Swedish troops re-occupied Swedish Pomerania and deployed against Napoleon's forces as a result of treaties between Charles John, on the behalf of Sweden, and the United Kingdom and Prussia, which ceded Norway to Sweden for is participation in the war becoming effective after France and its allies were defeated. In early December Charles John led an invasion of Denmark with his Allied Army of the North that included Swedes, Russians and North Germans. The Danes were outnumbered and were unable to mount a coherent defense against Bernadotte's battle-hardened army. Within a few days the Danes were forced out of Holstein and into the Jutland proper. By December 14 Bernadotte agreed to an armistice and peace talks began in Kiel on the basis of the cession of Norway to Sweden in return for Swedish Pomerania, additional territory in North Germany, specifics to be decided at the general peace conference following the cessation of hostilities between the Sixth Coalition and Imperial France, as well as 1,000,000 Riksdalers. The Danish position was hopeless and by early January 1814 the Danish King reconciled himself to the necessity of losing Norway By the Treaty of Kiel, signed on 13 January, King Frederik VI of Denmark-Norway had to cede Norway to the King of Sweden. However, this treaty was not accepted by the Norwegians who refused to be bartered about like so many chattels. Elements of the Danish Government also covertly supported Norway's determination to not be incorporated into Sweden. Ultimately, Denmark would pay a catastrophic price for its intrigues, as Bernadotte viewed this support, no matter how covert, as perfidy and a violation of the Treaty of Kiel, and this would later be reflected in the final peace crafted at the Congress of Vienna wherein the provisions to award Swedish Pomerania, along with various additional Northern German territory, as well as 1,000,000 Riksdalers to Denmark as compensation for its loss of Norway, were voided.
Norwegian Constituent Assembly
Prince Christian Frederick of Denmark, heir presumptive to the thrones of Denmark and Norway and Governor-general of Norway, took the lead in the insurrection, and he called for a constitutional assembly. This adopted the liberal constitution of 17 May, which also elected Christian Frederick as the king of an independent Norway. As the head of the new state, Christian Frederick desperately tried to gain support from the United Kingdom, or any of the other major powers within the Sixth Coalition, in order to maintain Norway's independence. However, the foreign diplomats gave no hope for any outside support to the Norwegians.
Armies
The Norwegian Army mustered 30,000 men, and it had taken up positions away from the border with Sweden, in the fear of being outflanked. The Norwegian navy had few vessels, and most of them were stationed at the islands of Hvaler, close to Sweden. The Swedish Army consisted of 45,000 men, experienced and well-equipped soldiers. The Swedish Navy had a number of large vessels and a capacity for moving and landing troops as well as assistance from the British Royal Navy.
The hostilities opened on 26 July with a swift Swedish naval attack against the Norwegian gunboats at Hvaler. The Norwegian army was evacuated and the vessels managed to escape, but they did not take part in the rest of the war. The main Swedish offensive came across the border at Halden, bypassing and surrounding the fortress of Fredriksten, and then continuing north, while a second force of 6,000 soldiers landed at Kråkerøy outside of Fredrikstad. This town surrendered the next day. This was the start of a pincer movement around the main part of the Norwegian army at Rakkestad. On the front towards Kongsvinger the forces were more evenly matched, and the Norwegian army eventually stopped the Swedish advance at Lier on 2 August, and won another victory at Matrand on 5 August. On 3 August, King Christian Frederick reached the front at Østfold and was persuaded to change his strategy and use the 6,000 men stationed at Rakkestad in a counterattack against the Swedes. The order to counterattack was given on the 5th of August, but the order was recalled a few hours later. The Norwegian forces therefore withdrew over the Glomma river at Langnes in Askim. The last major battle of the war was fought on 9 August at the bridgehead at Langnes, where the Swedish forces once more were driven back. Sweden then attempted to outflank the Norwegian line, and successfully did so during the battle of Kjølberg Bridge on the 14th of August. The Swedes then had a clear path to Kristiania, the Norwegian capital. In addition, the British blockade of Norway gradually worsened the Norwegians' situation, making food shortages common everywhere. The proximity of Swedish armies and the British blockade eventually made the Norwegians' situation unsustainable. Although the Norwegian Army had won at Langnes, it was nevertheless clear to both the Norwegian and Swedish military authorities that a defeat was inevitable. Even as they had managed to deliver several minor offensive blows to the Swedes, thus applying pressure on the Swedes to accept Norway as a sovereign nation, it was considered impossible to try to stop the Swedes in the long run. The Swedish offer of negotiations was therefore accepted as the war had put a heavy strain on the Norwegian finances. Every day of delay in securing Norway by the Swedes brought uncertainty to them regarding the outcome, so both parties were interested in a quick end to the war. For the ordinary Norwegian soldier the war had seemed ill-prepared and ill-fought. The allegations of the loss were against Christian Frederick and the Norwegian general Haxthausen; the latter was accused of treason. For the Norwegian government it probably had been more of a matter of getting the best possible bargaining position, as without the support of major powers Norway's independence was impossible to secure. But by agreeing to talks following the victory at Langnes they were in a situation where they could avoid an unconditional surrender.
Aftermath
On 10 August, Bernadotte presented a proposal for a cease-fire. The proposal included a major concession—Bernadotte, on behalf of the Swedish government, accepted the Eidsvoll constitution. In doing so, he tacitly gave up any claims that Norway would be merely a Swedish province. Negotiations started in Moss, Norway on 10 August, and after a few days of hard negotiations, a cease fire agreement, called the Convention of Moss, was signed on 14 August. King Christian Frederick was forced to abdicate, but Norway remained nominally independent within a personal union with Sweden, under the Swedish king. Its Constitution was upheld with only such amendments as were required to allow it to enter into the union, and the two united kingdoms retained separate institutions, except for the king and the foreign service and policy.
