The background of the Winter War covers the period before the outbreak of the Winter War between Finland and the Soviet Union in 1939–1940, stretching from Finland's Declaration of Independence in 1917 to the Soviet-Finnish negotiations in 1938–1939. Before its independence, Finland was an autonomous grand duchy inside Imperial Russia. During the ensuing Finnish Civil War, the Red Guards, supported by the Russian Bolsheviks, were defeated. Fearful of Soviet designs, during the 1920s and 1930s, the Finns were constantly attempting to align themselves with Scandinavian neutrality, particularly with regard to Sweden. Furthermore, the Finns engaged in secret military co-operation with Estonia in the 1930s.