In the early 1940s, between the Winter War and the Continuation War, tensions were high in Finland. The Soviets could invade, seemingly, at any moment. As a result, in 1940, Finland began the construction of Salpalinja (the “Salpa Line”), a system of more than 700 field fortifications made from concrete or excavated from rock along Finland’s eastern border. Stretching 1,200 kilometers (746 miles) from the Gulf of Finland in the south to modern-day Pechengsky, Russia, in the north, Salpalinja consisted of bunkers, trenches, fueling stations, weapons depots, and more. The line incorporated many…
