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 against the Soviet Union in the Winter War, which started on 30 November 1939. The war was a consequence of the Molotov–Ribbentrop Pact, which put Finland into the Soviet sphere of influence. 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.
The Winter War started in November 1939. 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. As 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.
Finland's defensive war against the Soviet invasion, lasting November 1939 to March 1940, came at a time when there was a military stalemate on the continent called the "Phony War". Attention turned to the Nordic theater. Months of planning at the highest civilian, military and diplomatic levels in London and Paris, saw multiple reversals and deep divisions. Finally, the British and French agreed on a plan that involved uninvited invasions of Norway, Sweden, Iceland, and Denmark's Faroe Islands, with the goals of damaging the German war economy and assisting Finland in its war with the Soviet Union. An allied war against the Soviet Union was part of the plan. The main naval launching point would be Royal Navy's base at Scapa Flow in the Orkney Islands. The Soviet invasion of Finland excited widespread outrage at popular and elite levels in support of Finland not only in wartime Britain and France but also in neutral United States. The League of Nations declared the USSR was the aggressor and expelled it. "American opinion makers treated the attack on Finland as dastardly aggression worthy of daily headlines, which thereafter exacerbated attitudes toward Russia."
The real Allied goal was economic warfare: cutting off shipments of Swedish iron ore to Germany, which they calculated would seriously weaken German war industry. The British Ministry of Economic Warfare stated that the project against Norway would be likely to cause "An extremely serious repercussion on German industrial output ... [and the Swedish component] might well bring German industry to a standstill and would in any case have a profound effect on the duration of the war." The idea was to shift forces away from doing little on the static Western front into an active role on a new front. The British military leadership by December became enthusiastic supporters when they realized that their first choice, an attack on German oil supplies, would not get approval. Winston Churchill, now head of the Admiralty, pushed hard for an invasion of Norway and Sweden to help the Finns and cut the iron supplies. Likewise, the political and military leaders in Paris strongly supported the plan, because it would put their troops in action. The poor performance of the Soviet army against the Finns strengthened the confidence of the Allies that the invasion, and the resulting war with Russia, would be worthwhile. However, the civilian leadership of Neville Chamberlain's government in London drew back and postponed invasion plans. Neutral Norway and Sweden refused to cooperate. 
Initial Allied approaches
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.
The Franco-British plan, as initially designed, proposed a defense of all of Scandinavia north of a line Stockholm–Gothenburg or Stockholm–Oslo, i.e. the British concept of the Lake Line following the lakes of Mälaren, Hjälmaren, and Vänern, which would provide a good natural defense some 1,700–1,900 kilometres (1,000–1,200 miles) south of Narvik. The planned frontier not only involved Sweden's two largest cities but could result in large amounts of Swedish territory being either occupied by a foreign army or becoming a war zone. The plan was revised[when?] to include only the northern half of Sweden and the narrow adjacent Norwegian coast.
The Norwegian government denied transit rights to the proposed Franco-British expedition.
The Swedish government, headed by Prime Minister Per Albin Hansson, declined to allow transit of armed troops through Swedish territory, in spite of the fact that Sweden had not declared itself neutral in the Winter War. The Swedish government argued that, since it had declared a policy of neutrality in the war between France, Britain and Germany, the granting of transit rights by Sweden to a Franco-British corps, even though it would not be used against Germany, was still an illegal departure from international laws on neutrality.
This strict interpretation appears to have been a pretext to avoid angering the Soviet and Nazi German governments.[according to whom?] Another interpretation was to deny the allies an opportunity to fight Germany far from England or France, destroying the Swedish infrastructure in the process.[according to whom?]
The Swedish Cabinet also decided to reject repeated Finnish pleas for regular Swedish troops to be deployed in Finland and the Swedes also made it clear that their present support in arms and munitions, could not be maintained for much longer. Diplomatically, Finland was squeezed between Allied hopes for a prolonged war and Swedish and Norwegian fears that the Allies and Germans might soon be fighting each other on Swedish and Norwegian soil. Norway and Sweden also feared an influx of Finnish refugees if Finland lost to the Soviets.
Fifteen months later, the Swedish government conceded to German demands for transit rights of one division across Sweden for German troops on their way from occupied Norway to Finland, in order to join the German attack on the Soviet Union. A total of 2,140,000 German soldiers on leave and more than 100,000 German military railway carriages crossed neutral Swedish territory during the next three years.
Further Allied proposals and their effect on peace negotiations
While Germany and Sweden pressured Finland to accept peace on unfavorable conditions, Britain and France had the opposite objective. Different plans and figures were presented for the Finns. France and Britain promised to send 20,000 men, who were to arrive by the end of February. By the end of that month, Finland's Commander-in-Chief, Field Marshal Mannerheim, was pessimistic about the military situation and, on 29 February, the government decided to start peace negotiations. That same day, the Soviets commenced an attack against Viipuri.
When France and Britain realized that Finland was considering a peace treaty, they gave a new offer of 50,000 troops, if Finland asked for help before 12 March. Finland hoped for Allied intervention but its position became increasingly hopeless; its agreement to an armistice on 13 March signalled defeat. On 20 March, a more aggressive Paul Reynaud became Prime Minister of France and demanded an immediate invasion; Chamberlain and the British cabinet finally agreed and orders were given. However, Germany invaded first, quickly conquering Denmark and southern Norway in Operation Weserübung, repelling Allied counter-efforts in Scandinavia. With the British failure in Norway, London decided it immediately needed to set up naval and air bases in Iceland. Despite Iceland's plea for neutrality, its occupation was seen as a military necessity by London. The Faroe islands were occupied on 13 April, and the decision made to occupy Iceland on 6 May.
- Plan R 4
- Operation Pike
- Allied campaign in Norway
- Foreign support in the Winter War
- Swedish iron mining during World War II
- Bernard Kelly, "Drifting Towards War: The British Chiefs of Staff, the USSR and the Winter War, November 1939–March 1940." Contemporary British History 23.3 (2009): 267–291.
- J. R. M. Butler, History of Second World War: Grand strategy, volume 2: September 1939-June 1941 (1957) pp 91–150. online free
- Gordon F. Sander, The Hundred Day Winter War (2013) pp 4–5.
- Butler, p 96
- Ralph B. Levering (2017). American Opinion and the Russian Alliance, 1939-1945. p. 210.
- Butler, p 97
- Erin Redihan, "Neville Chamberlain and Norway: The Trouble with 'A Man of Peace' in a Time of War." New England Journal of History (2013) 69#1/2 pp 1–18.
- National Archives and Records Administration: State Department and Foreign Affairs Records – Sweden
- Scandinavian Press, Issue 3 1995) Nordic Way Article
- Butler, pp 122–124.
- Bernard Kelly, "Drifting Towards War: The British Chiefs of Staff, the USSR and the Winter War, November 1939–March 1940," Contemporary British History, (2009) 23:3 pp 267–291, DOI: 10.1080/13619460903080010
- Butler, p 128.
- H.L. Davies, "Iceland: Key to the North Atlantic." Royal United Services Institution Journal 101#602 (1956): 230–234.
This article includes a list of references, but its sources remain unclear because it has insufficient inline citations. (July 2009) (Learn how and when to remove this template message)
- Butler, J. R. M. History of Second World War: Grand Strategy, volume 2: September 1939-June 1941 (1957) pp 91–150, 389–415, 465–486. online free
- Engle, Eloise & Paananen, Lauri (1992). The Winter War: The Soviet Attack on Finland 1939–1940. Stackpole Books. ISBN 0-8117-2433-6.
- Jakobson, Max (1961). The Diplomacy of the Winter War: An Account of the Russo-Finnish War, 1939–1940. Cambridge, MA: Harvard University Press.
- Nissen, Henrik S. ed. Scandinavia during the Second World War (Nordic Series, number 9.) (University of Minnesota Press and Universitetsforlaget, Oslo. 1983), 407pp
- Öhquist, Harald (1949). Talvisota minun näkökulmastani. Helsinki: WSOY. (in Finnish)
- Ries, Tomas (1988). Cold Will: Defence of Finland. Brassey's. ISBN 0-08-033592-6.
- Schwartz, Andrew J. (1960). America and the Russo-Finnish War. Washington, D.C.: Public Affairs Press.
- Tanner, Väinö (1957) The Winter War: Finland against Russia 1939–1940 Stanford University Press, California; also London.
- Trotter, William R. (2002, 2006) . The Winter war: The Russo–Finno War of 1939–40 (5th ed.). New York (Great Britain: London): Workman Publishing Company (Great Britain: Aurum Press). ISBN 1-85410-881-6.
First published in the United States under the title A Frozen Hell: The Russo–Finnish Winter War of 1939–40Check date values in:
- Upton, Anthony F. (1974). Finland 1939–1940 (University of Delaware Press, Newark: part of series The Politics and Strategy of the Second World War) ISBN 0-87413-156-1
- Van Dyke, Carl (1997). The Soviet Invasion of Finland, 1939-40. Frank Cass Publishers. ISBN 0-7146-4314-9.
- Vehviläinen, Olli (2002). Finland in the Second World War: Between Germany and Russia. New York: Palgrave. ISBN 0-333-80149-0.
- "Finland i Krig 1939-1940" – multiple authors. ISBN 951-50-1182-5