In the wake of the bloody civil war that followed Finland’s independence from Russia in 1917, the border between the two countries was established across the Karelian Isthmus, an area long fought over by Russia, Finland and Sweden in their attempts to dominate the northern tip of Europe. Neither the Soviets nor the Finnish were comfortable with such a divide which was only 32km from the military and industrial city of Petrograd. As such, both sides began an intensive period of fortification and defensive planning. As the Winter War broke out in November 1939, the complex and heavily defended Mannerheim Line suffered intense bombardment. The armistice of 1940 saw Finland cede control of the entire Karelian Isthmus to the USSR, and a propaganda war ensued. Through an analysis of the background, and operational history of the Mannerheim Line, Bair Irincheev attempts to dispel such myths and provide an accurate assessment of its huge historical importance.