How did the Russo-Finnish War affect Hitler’s view of Soviet military strength?

The early stages of the Russo-Finnish War (1939–1940) led Adolf Hitler and the Western democracies to significantly underestimate Soviet military capabilities. Because the Red Army initially struggled against Finnish forces and failed to quickly overcome the Mannerheim Line, Hitler perceived the Soviet military as weak and ineffective.1

This miscalculation contributed to the German belief that the Soviet Union could be defeated in a short campaign of two to three months. Hitler’s underestimation of the Soviet Union was further reinforced by political assumptions that the Soviet regime would collapse from a lack of domestic support shortly after a German invasion. These flawed assessments were central to the planning of Operation Barbarossa, as German leadership failed to account for the vast troop reserves and resilience that the Soviet Union would ultimately demonstrate.2