 Another source later used widely in Soviet historiography was Molotov 's speech in front of the Supreme Soviet on 29 March 1940 , in which he blamed Western countries for starting the war and argued that they had used Finland as a proxy to fight the Soviet Union . The Western Allies had furthermore tried to take neutral Sweden and Norway along with them . Thus , the " masterminds " behind the war were the UK and France , but also Sweden , the United States , and Italy , who had issued massive amounts of materiel , money , and men to Finland . According to Molotov , the Soviet Union was merciful in peace terms , as the problem of Leningrad security had been solved . 
