Previously posted at: https://www.history.com/this-day-in-history/ussr-attacks-finland
On November 30, 1939, the Red Army crosses the Soviet-Finnish border with 465,000 men and 1,000 aircraft. Helsinki was bombed, and 61 Finns were killed in an air raid that steeled the Finns for resistance, not capitulation.
The overwhelming forces arrayed against Finland convinced most Western nations, as well as the Soviets themselves, that the invasion of Finland would be a cakewalk. The Soviet soldiers even wore summer uniforms, despite the onset of the Scandinavian winter; it was simply assumed that no outdoor activity, such as fighting, would be taking place. But the Helsinki raid had produced many casualties-and many photographs, including those of mothers holding dead babies, and preteen girls crippled by the bombing. Those photos were hung up everywhere to spur on Finn resistance. Although that resistance consisted of only small numbers of trained soldiers-on skis and bicycles!–fighting it out in the forests, and partisans throwing Molotov cocktails into the turrets of Soviet tanks, the refusal to submit made headlines around the world.
President Roosevelt quickly extended $10 million in credit to Finland, while also noting that the Finns were the only people to pay back their World War I war debt to the United States in full. But by the time the Soviets had a chance to regroup, and send in massive reinforcements, the Finnish resistance was spent. By March 1940, negotiations with the Soviets began, and Finland soon lost the Karelian Isthmus, the land bridge that gave access to Leningrad, which the Soviets wanted to control.