Franco-British plans for intervention in the Winter War

During the early stages of World War II, the British and French Allies made a series of proposals to send troops to assist Finland in the Winter War against the Soviet Union which started on 30 November 1939. The war was a consequence of the Molotov-Ribbentrop Pact. The plans involved the transit of British and French troops and equipment through neutral Norway and Sweden. The initial plans were abandoned due to Norway and Sweden declining transit through their land, fearing their countries would be drawn into the war. The Moscow Peace Treaty ended the war in March 1940 precluding the possibility of intervention.

In February 1940, a Soviet offensive broke through the Mannerheim Line on the Karelian Isthmus, exhausting Finnish defenses and forcing the country's government to accept peace negotiations on Soviet terms. At the news that Finland might be forced to cede its sovereignty to the USSR, public opinion in France and Britain, already favorable to Finland, swung in favor of military intervention. When rumors of an armistice reached governments in Paris and London, both decided to offer military support.

The first intervention plan, approved on 4–5 February 1940 by the Allied High Command, consisted of 100,000 British and 35,000 French troops that were to disembark at the Norwegian port of Narvik and support Finland via Sweden while securing supply routes along the way. Plans were made to launch the operation on 20 March under the condition of a formal request for assistance from the Finnish government (this was done to avoid German charges that the Franco-British forces constituted an invading army). On 2 March, transit rights were officially requested from the governments of Norway and Sweden. It was hoped that Allied intervention would eventually bring the neutral Nordic countries, Norway and Sweden, to the Allied side by strengthening their positions against Germany—although Hitler had by December declared to the Swedish government that Franco-British troops on Swedish soil would immediately provoke a German invasion.

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