The Mainila Incident was an alleged artillery shelling of Soviet soldiers near the Soviet border village of Mainila, which occurred on November 26, 1939. The incident became the formal pretext for the Soviet-Finnish War of 1939.

According to official Soviet claims, on November 26, 1939, a group of Soviet servicemen was shelled by artillery from Finnish territory near the border section close to the village of Mainila. Seven artillery shells were fired, resulting in the deaths of three privates and one junior commander, and injuries to seven privates and two officers. These figures were presented in a Soviet note and an official report in the newspaper Pravda.

Presumably, the firing came from a Finnish anti-tank gun located near Yappinen, five kilometers from Mainila. This could have been one of the following types of guns: a 37-mm PstK/36 “Bofors” anti-tank gun, a 45-mm anti-tank gun, a Russian 75-mm model 1915 gun, or a 76.2-mm K02 gun (the Russian “three-inch gun”).

Regarding this shelling, the Soviet government addressed Finland with a note claiming that the shots were fired from Finnish territory. To prevent further provocations, the Soviets demanded that Finnish troops be withdrawn 20–25 km from the border.

In response, the Finnish government stated that, according to observations from Finnish sound-ranging posts, seven shots were fired around 4:00 p.m. from the Soviet side, approximately 1.5 to 2 kilometers southeast of the shell explosion site. It was also noted that the Finns simply did not have artillery on the border, especially long-range artillery. The Finns proposed forming a joint commission to investigate the incident and to begin negotiations on mutual troop withdrawals from the border. This proposal was rejected by the Soviet side. The refusal was justified by the fact that withdrawing Red Army units from the border by the requested distance would have placed troops in the suburbs of Leningrad, which was completely unacceptable for the city’s security.

According to the pro-Western version of events, the shelling was carried out by an NKVD special unit.

The result of the incident was an order to Soviet troops in the border area to respond to any aggressive actions by the Finns with fire, up to and including the destruction of the attackers. Two days after the incident, the USSR broke the non-aggression pact with Finland, and four days later, started the war.

Foreign historiography, particularly Finnish, views the incident as a deliberate provocation by the USSR aimed at obtaining a pretext to start the war. Contemporary historians close to the Russian government try in every way to justify the Soviet aggression.

The escalation of tensions on the border and the shelling of Soviet territory at that time did not serve Finland’s interests. For example, three months before the incident, Finnish Prime Minister Aimo Cajander stated at a review of Finnish reservists:

We are proud that we have little weaponry rusting in arsenals, little military equipment rotting and moldy in warehouses. But in Finland, we have a high standard of living and an education system we can be proud of.

Soviet historians, for their part, have never doubted that the shelling of Soviet territory by the Finns actually took place.

After the collapse of the USSR, several Russian researchers studied documents, including declassified Soviet archives related to this story. It was not possible to definitively confirm the fact of a deliberate provocation, but facts were found that make this version quite convincing.

According to historian Boris Sokolov, discrepancies were found in the numbers of wounded and killed Soviet servicemen cited in various documents; there is no named list of the victims; the incident is mentioned only in the combat log of the 68th Rifle Regiment, and all entries from November 1939 to March 1940 were made by the same hand (which suggests forgery), although during this period the regiment changed commanders and chiefs of staff four times, who were responsible for maintaining the combat log.

Sokolov also reports that in the operational summaries and reports compiled by the command of the 70th Rifle Division, which included the regiment, there are no records of shelling from the Finnish side, nor any indication of changes in personnel numbers, which indirectly supports the forgery theory.

According to historian Ivan Seydin, some authors have proposed a version in which the shelling was carried out by Soviet mortar crews from the positions of Soviet border troops or by army artillerymen, with target corrections directed by the Leningrad Regional NKVD administration.

Seydin also reports that handwritten notes by A. A. Zhdanov were discovered, which can be interpreted as a plan for a border provocation and its subsequent use for propaganda purposes.

The commander of the 7th Army at the time, Army Commander 2nd Rank Meretskov, described the event as follows: “On November 26, I received an urgent report stating that near the village of Mainila, the Finns opened artillery fire on Soviet border guards. Four people were killed, nine wounded.”

Regarding the events that led to the war, Mannerheim wrote:

…And here is the provocation I had expected since mid-October, fulfilled. When I personally visited the Karelian Isthmus on October 26, General Nenonen assured me that the artillery had been completely withdrawn behind the line of fortifications, from where no battery could fire beyond the border… On November 26, the Soviet Union organized the provocation now known as the “Shots at Mainila”… During the 1941–1944 war, Russian prisoners of war described in detail how the clumsy provocation was organized…

Many years later, the head of the Soviet Union, N. S. Khrushchev, stated that the shelling was carried out by Soviet troops under the command of Army Commander 1st Rank Grigory Kulik, but claimed that he did not know whether the first shots were fired by the Soviet or Finnish side.

Sources:

https://echo.msk.ru/blog/aillar/2546613-echo/

https://timenote.info/ru/events/proizoshjol-Majnilskij-incident-incident-stavshij-formalnim-povodom-dlja-nachala-Sovetsko-finskoj-vojni