The Treaty of Paris, signed on 6 January 1810, ended the war between France and Sweden after Sweden's defeat by Russia, an ally of France, in the Finnish War of 1808-1809. Russia had previously been an ally of Sweden in the Third and Fourth Coalitions against France, but after Russia's defeat at Friedland, she joined France and attacked Sweden so as to compel her to join Napoleon'sContinental System. Indeed, the primary result of the treaty was Sweden's agreement to join the Continental System, so that Sweden would not trade with the UK. Shortly after the treaty was signed, on 21 August 1810, one of Napoleon's marshals, Jean-Baptiste Bernadotte, was elected crown prince of Sweden, and he went on to found the House of Bernadotte, which remains the Royal House of Sweden. The peace resulting from the treaty lasted until Napoleon's refusal to permit Sweden to annex Norway, which was then under the sovereignty of Denmark, an ally of France. This was followed in January 1812 by French occupation of Swedish Pomerania for violation of the Continental System, since Sweden was still trading with the UK, and, in April, Sweden's conclusion of the Treaty of Petersburg with Russia against France.