Editing Gustav IV Adolf (section)

==Loss of Finland==
{{Main|Finnish War}}
His reign was ill-fated and was to end abruptly. In 1805, he joined the [[War of the Third Coalition|Third Coalition.]] 
against [[Napoleon]]. His campaign went poorly and the French occupied [[Swedish Pomerania]]. When his ally, Russia, made peace and concluded an alliance with [[Treaties of Tilsit|France at Tilsit]] in 1807, Sweden and [[Portugal]] were left as [[United Kingdom of Great Britain and Ireland|Great Britain]]'s only allies on the European continent. On 21 February 1808, [[Finnish War|Russia invaded Finland]], which was ruled by Sweden, on the pretext of compelling Sweden to join Napoleon's [[Continental System]]. [[Denmark–Norway|Denmark]] likewise declared war on Sweden.{{Citation needed|date=April 2007}} In just a few months, almost all of Finland was lost to Russia. As a result of the war, on 17 September 1809, in the [[Treaty of Fredrikshamn]], Sweden surrendered the eastern third of Sweden to Russia. Following which the autonomous [[Grand Duchy of Finland]] was established within [[Imperial Russia]].