Karelian Isthmus

The Karelian Isthmus is the narrow stretch of land between the Gulf of Finland and Lake Ladoga in northwestern Russia. The city of Vyborg and the town of Priozersk are situated on the northwestern end of the isthmus. In the southeast it reaches to Saint Petersburg. Since World War II, when the fronts moved back and forth over the isthmus, it belongs to the Leningrad Oblast of Russia.

Map of the Karelian isthmus. Shown are important towns, the current Finnish-Russian border in the North-West and the pre-Winter War border further South

1721-1812 the isthmus belonged to the Russian Empire, won in the Great Northern War. In the South, the new imperial capital for Russia, Saint Petersburg, had been founded in 1703. Then the northwestern half was transferred, as a part of Old Finland, to the semi-autonomous Grand Duchy of Finland, since 1809 in personal union with Russia.

Due to the rich soil, rich fishing waters and the proximity to Saint Petersburg, the Karelian Isthmus became the wealthiest part of Finland once the industrial revolution had gained momentum in the 19th century. When Finland declared its independence in 1917, the isthmus remained Finnish.

In November 1939, the Soviet Union invaded Finland in what became known as the Winter War. Soviet forces were able to penetrate through the well-defended Mannerheim Line across the isthmus in early 1940. Finland ceded the Karelian isthmus to the Soviet Union in the Peace of Moscow.

One year later, in 1941 when Germany invaded the Soviet Union in the Operation Barbarossa, which led to the Great Patriotic War for the Russians and the Continuation War for the Finns, Finland could initially retrieve the lost territory (co-belligerent with Nazi Germany) making halt first at the Russian side of the border of 1939, thereby by the Russians seen as indirectly contributing to the Siege of Leningrad.

On 9 June, 1944, strong Soviet forces opened a counter-offensive and pushed the front from Leningrad to Vyborg in ten days. In the Battle of Tali-Ihantala, 25 June–9 July, the Finns concentrated their military strength and brought the offensive to halt at the River Vuoksi, in the northwesternmost part of the isthmus — close to the border of 1940, that again was recognized by Finland in the Peace of Paris, 1947. Since then the isthmus has belonged to the Leningrad Oblast.