Mannerheim Line

The Mannerheim Line, a defensive position emplaced by Finland to defend itself against invasion from the Soviet Union, stands in great contrast to many other defensive systems. It represents both the lowest level of investment of many of other barriers and the highest level of strategic success, as manifested by its performance in the Russo-Finnish "Winter" War of 1939-1940.

The beginnings of what came to be called the Mannerheim Line arose from the aftermath of World War I, when portions of the Russian Empire, including Finland, broke away from Russian control after the revolution of 1917 and the Russian collapse under German military pressure. In the early 1920's, the resurgent Bolsheviks attempted to regain control of former fringe provinces in Europe and in Asia, and in some cases were successful in doing so [eg, Ukraine]. Newly independent Finland sought to prevent such reabsorption into the new Soviet Empire by maintaining effective, if small, armed forces and by supplementing them with defensive obstacles placed at key chokepoints in the difficult Finnish terrain of lakes, forests, tundra, and swamps. The worldwide tensions of the late 1930's affected Russo-Finnish relations as well, and Russians threats, demands, and ultimata prompted the Finns to refurbish these defenses prior to the actual Russian attack in 1939.

The Soviet invasion was, in general, poorly prepared and poorly executed. Although the Soviet border with Finland was nearly 1,000 miles in length, and the Soviets frittered away much of their logistic resources in worthless attacks against much of this long border with its nearly impassable and unpopulated areas, the one key region lay near the Gulf of Finland where the important Soviet city of Leningrad and the Finnish capital of Helsinki were separated from each other by only 150 miles. The relatively narrow isthmus between Lake Ladoga and the Gulf of Finland was the only feasible corridor for a land attack on Finland; it was the area where the Finns placed their greatest defensive effort; and it was where the Soviets concentrated their major assaults.

The Mannerheim Line was a relatively small scale effort consisting of simple tactical obstacles designed to slow a Soviet attack, protect Finnish defenders, and cause increased Soviet casualties. Because Finnish resources were so small in comparison to that of the Soviet Union, with apopulation ratio of 1:50 versus their eastern neighbors, the Finns could not, and did not, delude themselves into believing that any barrier they could construct would either deter the Soviets from attacking or would stop a Soviet attack once launched. Finnish hopes for deterrence or survival rested more strongly on the overall balance of power between the Soviet Union and other countries than on their own resources.

Ironically, however, this defensive system, constructed for tactical reasons and used as a tactical resource, did achieve a greater strategic success than many other barriers. The many thousands of casualties and months of delays suffered by the Soviets in the assaults on the Finnish positions, coupled with other international developments, were so great that the Soviets scaled back their war aims significantly, allowing Finland to survive as a viable country with most of its territory still intact. The energetic Finnish defense of a relatively meager defensive line, strengthened by easily defensible terrain, achieved results far in excess of other barriers, incomparably more expensive but less effectively utilized.