On November 26, 1939, the Soviets faked the Finnish shelling of the Russian town of Mainila. In the aftermath of the shelling, they demanded that the Finns apologize and withdraw their forces 25km from the border. Denying responsibility, the Finns refused. Four days later, 450,000 Soviet troops crossed the border. They were met by the small Finnish army which initially numbered only 180,000. The Finns were badly outnumbered in all areas during the conflict with the Soviets also possessing superiority in armor (6,541 to 30) and aircraft (3,800 to 130).
The Winter War proved a costly victory for the Soviets. In the fighting, they lost approximately 126,875 dead or missing, 264,908 wounded, and 5,600 captured. In addition, they lost around 2,268 tanks and armored cars. Casualties for the Finns numbered around 26,662 dead and 39,886 wounded. The Soviet's poor performance in the Winter War led Hitler to believe that Stalin's military could be quickly defeated if attacked. He attempted to put this to the test when German forces launched Operation Barbarossa in 1941. The Finns renewed their conflict with the Soviets in June 1941, with their forces operating in conjunction with, but not allied to, the Germans.