Finland Holds Off the Red Army in the Winter War

On 30 November 1939, the Soviet Union launched an invasion of Finland, initiating the conflict known as the Winter War three months after the outbreak of World War II. Soviet leadership had grown concerned over the proximity of the Finnish border to Leningrad, located only 32 kilometres away. During bilateral negotiations in late 1939, Soviet representatives demanded that Finland cede strategic territory on the Karelian Isthmus, dismantle fortifications, and lease the Hanko Peninsula for a naval base in exchange for territory elsewhere. Fearing for its national sovereignty and unwilling to grant military bases on its territory, the Finnish government rejected the revised terms, precipitating an impasse and a subsequent breakdown in diplomatic discussions.

Tensions peaked on 26 November when artillery fire was reported near the Soviet border post of Mainila. Soviet officials accused Finland of carrying out the strike, which allegedly killed four border guards, and used the incident as a pretext to renounce the mutual non-aggression pact. While official Soviet accounts maintained for decades that Finland was responsible, historians now broadly agree that the shelling was a false-flag operation staged by the Soviet side to manufacture a formal reason for invasion. Diplomatic ties were severed immediately, and Red Army divisions crossed the frontier days later.