Drawing borders with swords and scimitars
Archaeological finds show that Karelia has been inhabited for at least 6,000 years. No one knows for sure who the earliest inhabitants were, but those who have lived there in historical times have always been Finns or their close kith and kin. Borders entered the scene a lot later than people. In the case of Karelia - and also of Finland as a whole - they have changed dramatically many times in the course of the turbulent centuries.
The border drawn in the Peace of Pähkinäsaari between Sweden and Novgorod (a Russian city-state) in 1323 cut through Karelia and even Finland as we know it today all the way to the Gulf of Bothnia. Another treaty signed at Stolbova in 1617 left Sweden with roughly as much of Karelia as lay within Finland at the outbreak of the Winter War in 1939. In the Great Northern War, which lasted over 20 years and ended when a peace treaty was signed in Uusikaupunki in 1721, Sweden ceased to be a great European power and lost, along with a lot of other real-estate, Karelia to Russia. War erupted again a couple of decades later and this time the treaty that ended it, in 1743, moved the border even further west, as far as the River Kymijoki. During the long period of peace that then followed, conditions in Karelia remained much the same as they had been under Swedish rule and Swedish remained the most commonly-used language of administration. The next round of fighting went even worse for Sweden, which lost the whole of Finland to Russia. Now the border between the rival powers was in roughly the same place as it is between Finland and Russia today. In 1809 Czar Alexander I declared Finland an autonomous grand duchy, and transferred Karelia to it in 1812. Finland declared independence in 1917 and this was recognised by Soviet Russia. After the First World War, Finland signed a peace treaty with the Soviet Union at Tartu (Dorpat) in Estonia in 1920. Of the territories that she had captured, Finland handed over Repola in Karelia and received Petsamo on the Arctic Ocean in return. Under the terms of the 1940 Moscow peace agreement after the Winter War, Karelia had to be handed over to the Soviet Union.
Later during the Second World War, Finland was a co-belligerent of Germany in fighting against the Soviet Union and managed to retake Karelia. When the Red Army launched a massive onslaught towards the end of the war, its advance was stemmed on the Karelian Isthmus and Finland escaped occupation, but the war had been lost. Karelia along with Petsamo had to be ceded to the Soviet Union. The present border between Finland and Russia was determined in the 1947 Paris Peace Treaty.