On this day in 1920, Finland and the Soviet Union entered into the Treaty of Tartu which fixed Finland's first post war borders with Soviet Russia. This came in the context of ending the Heimosodat, a Finnish sponsored effort in the Finnish regions of Russia that sought to join the land inhabited by Russian Baltic Finns with Finland.
The story is complicated as the entire story involves a series of wars including wars of independence in neighboring states that were formerly part of Imperial Russia. In some instances Finnish volunteers sought to aid independence movements in hopes of a friendly state being established, in others they hoped for outright annexation of Finnish lands that lay inside of Russia's boundaries. The entire matter demonstrated, as the wars of the Poles we've recently dealt with, that former European imperial boundaries were rarely ethnic ones.
Finland itself occupies about 60% of the landmass inhabited by the Baltic Finns. Estonia is the second state that has a Baltic Finn population, with Estonians also being Baltic Finns, but Baltic Finns speaking a branch of the overall Finnish language. Finns from Finland sent volunteer units into Estonia to support it independence movement, which was successful at the time, a fairly remarkable thing to do as it was more or less concurrent with the Finnish Civil War.
Finnish volunteers in Estonia.
More serious, from a Russian prospective, were a series of Finnish supported efforts to secure the annexation of the large Finnish landmass to Finland's east. This lead to a complicated series of wars, the Heimosodat, that are now largely forgotten outside the region but which form an important aspect of the situation from that point forward.
From March 1918 until October 1918, Finnish volunteers attempted, and nearly succeeded, in taking Karelia from Russia. They were defeated not by Russian troops, with Russia collapsing into civil war at the time, but by British ones who feared the Germans securing access to the White Sea. Conservative Finns, the Finnish Whites, had support from Imperial Germany and the British saw the Finnish effort in that context. British efforts successfully caused the Finnish advance to fall apart and the Finns ultimately retreated. Following that, the British attempted unsuccessfully to sponsor Karelian independence.
Murmansk Legion, a British organized and equipped Finnish unit in Karelia that fought the Finnish volunteers in that region. The unit was made up of, in part, refugee Finnish Red Guards, making it essentially a Finnish communist unit organized to fight the Finnish whites in Karelia. When the British left Russia in 1919, many of its members went to Canada, with some securing reentrance to a less than enthused Finland. Some officers stayed in Soviet Russia and would later fight for the reds in the Spanish Civil War.
Also in 1918 Finnish volunteers attempted to annex Petsamo, the large northern landmass bordering the Arctic Sea, but were also pushed back by the British.
Finnish volunteers in Petsamo in 1918.
Finnish volunteers tried again for Karelia in 1919 in the Aunus expedition, now that Russia was fully in turmoil. The plan depended upon a Karelian uprising that didn't materialize, and after two months it retreated back into Finland.
In 1920 they also tried for Petsamo again, but were pushed back this time by Soviet troops.
In 1920 an uprising in North Ingria, the southern part of Karelia, ended up establishing a putative independent state that had the goal of being annexed to Finland, but which would have required the balance of Karelia to join Finland in order to succeed.
The Treaty of Tartu largely followed the former Imperial Russian boundaries of the Grand Duchy of Finland, excepting that the Finns received a portion of Petsamo including a port, which had been promised to them by the Imperial Russian government in 1864. They withdrew from some territory taken in in the other expeditions and abandoned support for North Ingria. The treaty largely held until the Soviet's unwarranted invasion in 1939 although the Finns supported an uprising in Karelia in 1921-22 which severely strained their relations with the USSR at the time.
The entire matter is another example of the mess of imperial boundaries and the complicated nature of the break apart of imperial regimes. By and large, Finns who dreamed of incorporating all Finnish lands into their newly independent state were justified in that goal. Imperial Germany ironically ended up supporting their aspirations and the British helped crush them. German support of Finnish whites helped prevent Finland from becoming a Soviet state that would have been annexed to the Soviet Union in the 1920s, but its probable that had the Finns succeeded in establishing themselves beyond their imperial boundaries the Soviets would have taken that territory back in any event, and perhaps the rest of Finland as well. At any rate, a good deal of Finnish ethnic territory remains outside of modern Finland today, and the territory, such as it was, that was gained by Finland in the Treaty of Tartu was lost at the end of the Continuation War.
