Finland–Russia border

The first treaty concerning the border was signed in Nöteborg in 1323, between Sweden (to which Finland belonged) and the Novgorod Republic. The Treaty of Teusina in 1595 moved the border eastward. As a result of the Ingrian War, Sweden gained a large tract of land through the acquisition of the Nöteborg fortress, the Kexholm and its large province, southwest Karelia and the province of Ingria in the Treaty of Stolbovo (1617). The Treaty of Nystad in 1721 and the Treaty of Åbo in 1743 moved the border westward.

The region surrounding the border was characterized by religious differences. The Russian side was predominantly Orthodox, while the Swedish side was initially Catholic, and later, Lutheran Protestant. Generally the native population was ethnically Finnish and Finnish-speaking immediately on both sides of the border. However, after the peace of Stolbovo in 1617, the Orthodox population faced persecution and many fled to Tver or converted to Lutheranism. Consequently, many started speaking Finnish instead of the closely related Karelian. The displaced population was largely replaced by immigrants from Finland, most of whom were Savonians.

After the Finnish War, the Treaty of Fredrikshamn converted all of Finland from Swedish territory to a Russian possession, the Grand Duchy of Finland. In 1812, the Finnish–Russian border reverted to its pre-1721 location, granting the Grand Duchy so-called "Old Finland" territories previously held by Sweden.

Treaty of Tartu in 1920: Repola and Porajärvi, occupied by the Finnish government, were returned to the Soviet Union, while Petsamo was gained by Finland.

In the period following Finland's 1917 independence declaration, during the Finnish Civil War and Russian Civil War, Finnish activists often crossed the border into Soviet territory in order to fight in the "heimosodat" wars surrounding Finnish ethnic self-determination and possible annexation into Finland. This ended in 1920 when the Russian/Finnish Treaty of Tartu in 1920 defined Finland as independent and established the countries' common border. Despite this, Finnish fighters took part in the East Karelian uprising and Soviet–Finnish conflict of 1921–22. In 1922, the Finnish government closed the border from the volunteers and food and munitions shipments.

Territorial losses of Finland to Soviet Union in conclusion to World War II; Porkkala was returned in 1956.

During World War II, Stalin severely suppressed the native Finnish-speaking population (Ingrian Finns) by population transfers, collectivization and purges.

In 1939, the USSR invaded Finland in the Winter War, leading to the signing of the Moscow Peace Treaty the following year. The treaty had Finland cede several border areas to the USSR.

After the Continuation War (1941–44), the land border was demarcated in the Treaty of Paris (1947). As a result, approximately half of Finnish Karelia (including Finland's fourth-largest city Vyborg), parts of Salla, and all of Petsamo were ceded to the Soviet Union. The new border cut through Finnish territory, severing many rail lines and isolating many Karelian towns from Finland. The Soviet Union demanded the territories be emptied, and Finns were subsequently evacuated from the area and resettled in Finland as almost no one was willing to stay. The areas were then resettled by Soviet immigrants. The Porkkala naval base was leased by the Soviet Union, but it was returned to the Finnish government in 1956. The naval border was established in 1940 and more accurately defined in 1965.

The border is uncontroversial and clearly defined by law.[8] Both states verified the inviolability of borders and territorial integrity in the first Conference on Security and Co-operation in Europe in 1975.

Border zone in 1967

During the Cold War, the border constituted part of the perimeter of the Iron Curtain. Crossing the border was not possible for much of its length. Only a very limited number of border crossing points existed, and the Soviet government permitted only escorted trips to select cities; border zones were off limits to tourists.[9] There was little contact between cities that were relatively close to each other on opposite sides of the border, such as Imatra and Svetogorsk. On the Finnish side, there was a border zone where entry was allowed only with a permit, but habitation was permitted and residents could continue living in the area. The Soviet side had extensive electronic systems and patrols to prevent escapes. Soviet border surveillance began at a great distance from the actual border, and was as extensive as elsewhere along the Iron Curtain. The first surveillance was already in railway stations in cities, where the militsiya monitored potentially suspicious traffic. The border zone began at 120 kilometres (75 mi) from the border. A special permit was required for entry, and the first line of control had electronic alarms. At 60 kilometres (37 mi), there was a raked sand strip (to detect footprints) and a thin alarmed tripwire. At 20 kilometres (12 mi), there was a 3 metres (9.8 ft) tall barbed wire fence, with a top that curved inwards towards Soviet territory (to keep people from leaving the USSR). The fence had an electronic alarm system. However, it was not protected underground and tunnelling under it was possible. Finally, at the international border, there was a border vista. In the north, this was followed by a Finnish reindeer fence. Unlike other Western countries, the government of Finland did not protect illegal border crossers but returned them to the Soviet authorities if captured. Illegal border crossers had to get through Finland to e.g. Sweden in order to defect to the West.[9]

In the Moscow Armistice signed in 1944 between Finland, the Soviet Union and the United Kingdom, a small peninsula towards the Gulf of Finland, Porkkala, was rented to the Soviet Union as a military base. This created in effect a southern border crossing to the Soviet exclave, operating all the way to 1956. Border crossings were in Luoma (checkpoint) and Tähtelä. In 1947, Finnish trains were allowed to pass through the base, but the passenger car windows were blinded and locomotive replaced while crossing through. Earlier between 1940 and 1941, the Soviet Union had rented Hanko Peninsula as a military base. Apparently there was also a border crossing to the exclave at the time.