Scandinavia
1939–1940: The Winter War
November 1939 – March 1940 · 5 battles
After the partition of Poland and the imposition of bases on the Baltic states, Stalin demanded territorial concessions from Finland on the Karelian Isthmus and a base on the Hanko peninsula. When the Finns refused, the Red Army attacked on 30 November 1939 without a declaration of war. The small Finnish army, defending the Mannerheim Line and the forests of Karelia, inflicted huge losses on the invader and for three months held off an enemy many times stronger. The Moscow peace of March 1940 cost Finland a tenth of its territory but saved its independence, and the weakness of the Red Army confirmed Hitler in his belief that the USSR could be defeated quickly.
- 30 November 1939 – 13 March 1940Key battleWinter WarFrom 30 November 1939 to 13 March 1940 Finland fought off the USSR. The Red Army broke the Mannerheim Line, but the Finns kept their independence.
- 7 December 1939 – 13 March 1940Battle of KollaaFrom 7 December 1939 to 13 March 1940 the Finnish 12th Division held the Kollaa river in Ladoga Karelia against the Soviet 8th Army until the peace.
- 7 December 1939 – 8 January 1940Battle of SuomussalmiFrom 7 December 1939 to 8 January 1940 Colonel Siilasvuo's Finns encircled and destroyed two Soviet divisions at Suomussalmi and on the Raate road.
- 1–17 February 1940Key battleBreaking of the Mannerheim LineIn February 1940, after ten days of bombardment, the Red Army broke the Mannerheim Line at Lähde and Summa. The Finns fell back to the intermediate line.
- 28 February – 13 March 1940Battle of Viipuri (1940)From 28 February to 13 March 1940 the Red Army stormed Viipuri and crossed the ice of Viipuri Bay. The city held, but the Finnish defence was near collapse.