→Factors in the Finns’ Favor
Besides Mannerheim’s superb approach to the war, the Finns were blessed with a government that did not micromanage the field marshal or his other commanders. The government let the commanders decide the course of the battle, which translated into battlefield daring and creativity. Along with a sympathetic government, the Finnish population overwhelming supported the war effort – even leftists who may have normally supported the Soviet Union fought alongside far-right nationalists on the Mannerheim Line in order to stem the Soviet tide.
The Finns hoped that ultimately their efforts to slow down the Red Army would send a signal to the world that some countries, even some the smallest, would take a stand against totalitarianism. Much of the Western press was sympathetic to the Finnish cause and when it seemed as though hostilities would break out, thousands of volunteers streamed into the Nordic nation to fight alongside the Finns on the Mannerheim Line. The major Western powers, though, remained reticent. The United Kingdom and France never declared war on the Soviet Union, even after the invasion of Poland, but a plan was developed to militarily aid the Finns in what became codenamed “Avonmouth.”
The French in particular embraced the plan enthusiastically, which was more about depriving Germany of iron-ore resources in neutral Sweden than it was about saving democratic Finland from the communist Soviet Union. Despite many in the French military openly advocating for Avonmouth, such as general Audet, the British never came on board and so the threat of foreign intervention on Finland’s behalf remained a threat, although a credible one that may have caused the Soviet high-command to make more measured moves. <ref> Cairns, John C. “Reflections on France, Britain and the Winter War Prodrome, 1939-40.” <i>Historical Reflections/Réflexions Historiques</i> 22 (1996) p. 212</ref>
In terms of battlefield tactics, Mannerheim and his commanders knew that they were at a supreme disadvantage in terms of numbers and equipment so they were forced to be creative and work with what they had. The topography of Finland is perfect for a defensive war and the
exceptional hearty and outdoor-centric Finns used that to their advantage. Finland is full of forests and doted throughout with lakes of various sizes. The heavy forest areas, especially north of Lake Ladoga, proved to be nearly impossible for Soviet tanks and mechanized vehicles to traverse when the Finns sabotaged the roads and the frozen lakes, which the Soviets thought were viable alternatives to the roads in the early stages of the war, proved to be death traps for Red Army columns when the Finns dynamited them sending many Soviet soldiers to frozen, watery graves. Although several battles took place throughout the northern Finnish-Soviet border, most of the action happened on the narrow land mass known as the Karelian Isthmus.
When planning for a potential Soviet invasion months before the Winter War, Mannerheim correctly deduced that the main thrust of the Soviet attack would come north from Leningrad (St. Petersburg) into the Karelian Isthmus towards the Finnish city of Viipuri/Viborg. The Karelian Isthmus is a narrow strip of land, only about 100 miles at its widest point, between Lake Ladoga in the north and the Gulf of Finland to the south. Hundreds of lakes dot the landscape, which Mannerheim knew would prove the perfect spot for a bottleneck. Between the lakes of the Karelian Isthmus, a series of bunkers, pillboxes, trenches, and stretches of barbed wire were erected in order to slow down the Red Army. The fortifications became known collectively as the Mannerheim Line for the commander who envisioned it.