Finnish–Estonian defence cooperation

Finnish–Estonian defence cooperation began in 1930 with a secret military pact between Finland and Estonia against the threat of the Soviet Union. Open cooperation ended in 1939, as the Soviets pressured the Estonian government, but it continued secretly with information-sharing during the Winter War.

The origins of defence cooperation lay in the Baltic Entente of the 1920s. Practical cooperation began with the initiative of the Finnish general staff in February 1930 in Tallinn, and the first joint war games were held in 1933. Officially both countries were neutral, but behind the scenes the relationship was more complex. Nazi Germany, for example, unsuccessfully offered Estonia a secret military alliance in 1937.

Finland started cooperation only for its own defensive reasons, despite both countries speaking the same Finnic languages and being neighbors. There were defense plans involving Finland launching a massive assault against Leningrad if the Soviet Union started a war against both countries. However, the plan would also have required the participation of Latvia, and according to the Finnish military leader, Carl Gustaf Emil Mannerheim, the countries would have needed outside help from the League of Nations. Finland could not send troops directly to the Baltic countries, but a joint assault would have been possible through the Karelian Isthmus and/or from Poland.

Before the 1930s, defence cooperation between Finland, Poland, Estonia, Lithuania, and Latvia was based on the Edge State Policy. In the 1930s this cooperation decreased, when Finland and Estonia started practical military dialogue. Due to the Finnish policy of neutrality and the official trend in the Nordic countries, the two nations kept their cooperation pact secret.

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