How did Finnish soldiers prevent the Soviet army from invading Finland with a simple trick?

The Soviet Army was unable for months to cross the Mannerheim Line and incurred heavy human losses

. 3 months after the start of the German invasion of Polish lands and the outbreak of World War II, the Soviet Union engaged about half a million soldiers to confront Finland in the Winter War that erupted on November 30, 1939 after the collapse of Negotiations between the two parties in which the Soviets demanded the Finns to hand over a number of areas with the aim of securing the city of Leningrad from the danger of a future German invasion.

In the midst of this war, which lasted until mid-March 1940, the Finns were able to hinder the progress of the Red Army and inflicted it heavy losses, as the number of Soviet dead and missing exceeded the threshold of one hundred thousand soldiers. Meanwhile, a series of defenses built at the Karelian Isthmus, known as the Mannerheim Line, played an important role in repelling the Soviets, as these Finnish defenses held back the Red Army's advance for months.

Create a Mannerheim line

With the declaration of Finland's independence in 1917, Finnish Russian officials ranked the Soviets as the most important threat to their country in the future. In addition, the military in Finland considered the Karelian Isthmus as the most important area through which the Soviet army might intervene in Finnish territory. While the eastern region of the Karelian Isthmus was considered safe thanks to the presence of an important part of the rugged natural terrain, the western part of it was classified as a sensitive site that the Red Army might exploit in the future to attack Finnish lands.

By May 1918, the Commander of the Armed Forces of Finland, Marshal Carl Gustaf Emil Mannerheim, assigned Swedish Lieutenant A. Rappe the task of creating a defensive line at the Karelian Isthmus. Based on RAP's plan, it was decided to build defensive fortifications to protect two railways near the border with the Soviet side. However, Raab's plan was abandoned a few months later, with the resignation of Marshal Mannerheim from his post.

During the month of July 1918, the Finnish military command approved a new defense plan presented by German Colonel O. von Brandenstein and allocated an amount of 300,000 marks to it. According to this plan, von Brandenstein proposed relying on the natural terrain to support the defenses of the Karelian Isthmus. But with the end of World War I and the defeat of Germany, work around the Karelian defensive line was halted before resuming months later.

With General Oscar Enckell taking command of Finland's armed forces, the Finns returned to building a line of defense in the Karelian Isthmus based on von Brandenstein's designs. In addition, the officials in Finland resorted to relying on the experience and advice of the French, in addition to a number of former soldiers in the army of Tsarist Russia.

Work continued on the construction of this defensive line, which was later called the Mannerheim Line after Marshal Carl Gustav Emil Mannerheim, who led the Finnish army in the Winter War, for about twenty years, divided into two periods, where the works initially extended between 1919 and 1924 before they resumed again in 1932 and ended 1939. In

addition, the Mannerheim Line included many reservoirs, also known as casemate, built of concrete, trenches and other fortifications designed to withstand artillery bombardment and equipped with machine guns.

hindered the advance of the Soviet army

During the Winter War, the Mannerheim Line obstructed the Soviet advance for more than two months as the Red Army forces were unable to cross it and incurred heavy losses, estimated at tens of thousands of soldiers, near it.
Hoping to calm the country's public opinion and reassure them of why the Red Army had failed in the Karelian Isthmus, the Soviet propaganda machine talked about the presence of massive defenses and artillery weapons, likening it to the Maginot Line, which France had built to protect itself from a future German military attack. In reality, however, the Mannerheim Line was a simple defensive line that remarkably lacked artillery against the Soviet forces.

With the end of the Winter War and the Finns accepting the Moscow Agreement, the Soviet Union sent teams of engineers toward the Karelian Isthmus to destroy what remained of the Mannerheim Line's defenses.