The lead up to the battle began in the 1930's as the Soviet Union annexed the Baltic nations of Latvia, Lithuania and Estonia. Then in 1939 as part of the none aggression pact signed by the Soviet Union and Germany she annexed the eastern half of Poland. Following this Stalin turned his attention on Finland. After talks failed to resolve the issue of the border being so close to Leningrad the USSR and Finland went to war on the 30th of November 1939.