Shelling of Mainila

The Soviet Union declared that the fire originated from Finland across the nearby border and claimed to have had losses in personnel.

Through that false flag operation, the Soviet Union gained a great propaganda boost and a casus belli for launching the Winter War four days later.

Earlier in the same year, Nazi Germany had staged the similar Gleiwitz incident to generate an excuse to withdraw from its nonaggression pact with Poland.

[6] Materials in the private archives of Soviet party leader Andrei Zhdanov show that the incident was orchestrated to paint Finland as an aggressor and launch an offensive.

[12] During the Continuation War, the 18th Division of the Finnish Army reached Rajajoki on 31 August 1941 and started preparations for taking the village of Mainila.

Location of Mainila on the Karelian Isthmus shown in relation to the pre-war Finnish-Soviet border.
Foreign journalists in Mainila on 29 November 1939.
Men of the 18th Division of the Finnish Army writing an 'address' on shells on 31 August 1941 before the 1941 shelling of Mainila