Finland’s Plans for the Winter War

When most people talk about Finland’s actions during the Winter War, they talk about agile white clad ski soldiers cutting through packed Soviet columns, gunning as they go. The meme of the Winter War being nothing more than farmers with skis using hit and run tactics isn’t wholly inaccurate but it isn’t entirely correct either. North of Lake Ladoga, the stereotypical image of Finns ambushing Soviet columns was a common occurrence due to the terrain and lack of resources. However, on the Karelian Isthmus, a more conventional war was being fought and despite the bloodiest battles being fought here, it seems to be often forgotten when the topic is discussed.

Evolution of Finland’s defensive plans

Soon after the victory during the Finnish Civil War, the victorious ‘whites’ set about creating a more permanent peacetime military force. As the devastation of the Civil War was still fresh, the Russian Civil War was raging right across the border and most of Eastern Europe was experiencing conflict, it was decided to stick with conscription. Conscription would allow for a large number of troops to be trained or ready in case of war, while having a professional carde would allow experience leaders to be in place.

While the new republic found itself in a difficult position during its first few years, it wouldn’t be until after the Treaty of Tartu and the formation of the Soviet Union that the Finnish military started to make plans regarding an invasion from the East. Several studies and exercises were held during the 1920s which played out scenarios of a Soviet invasion and it soon became apparent that the main focus of any Soviet attack would be through the Isthmus. Finland, however, wasn’t a rich nation and the subsequent governments placed the needs of the military secondary to social reforms. At first, this created a large gap between the military leadership and political elite and it wasn’t uncommon for there to be several heated debates during sessions for budget allocation. Yet, this focus on social reform worked in the military’s favour in the long run by creating the conditions for a more fair, unified and healthy population that was willing to defend their nation.

The majority of Finland’s artillery corps was made up of turn of the century guns like this French de Bange 155 mm long cannon mle. 1877. source: SA-Kuva

Throughout the inter-war years, Finland’s defensive strategy hinged upon two main points, budget and geography. The budget constantly fluctuated during the 1920s and early 1930s between 15 and 20%, it wouldn’t be until tensions rose across Europe that the Government poured more money into military spending. This wasn’t without consequences though, the Navy managed to lobby for a large percentage of the allocation many times, and while this did allow Finland to build two large coastal defence ships, acquire several submarines and upgrade some of their older vessels, it can be argued that this was more a waste of precious resources. The Air Force, which anti-aircraft defence also fell under, was having to make do with around 20% of the allocations, this meant that when the war broke out, it had only a handful of modern AA guns and a motley collection of aircraft. So with the instability of budget, the military staff concentrated upon the geography, as that was predictable.

The coastal defence ships Väinämöinen in Åland, January 1940. Source: SA-Kuva

The Karelian Isthmus – The Gateway to Helsinki

It was clear from several war games that any real assault against Finland from the east would be through the Karelian Isthmus. It was relatively flat, contained enough infrastructure not far from the border to sustain a large army, was the shortest route to Helsinki. An aggressive, combined arms strike in the late spring could effectively smash through any Finnish defences, thought Finnish high command. With this clear direction in mind, a programme to build a fortification line stretching across the Isthmus was started in 1920 and continued right until the Winter War. Officially called the Main Defence Line, this 140km long defensive line was more a scattering of about 188 defensive positions of various grades. According to inspection reports carried out just before the war, there was only 26 in sufficient state, while another 49 were of inferior quality, another 40 were considered too old to be of any use. However, it wasn’t the quality of the positions that would be the saving grace, but the usage of them.

Plan for one of the more modern types of bunkers for the main defence line. Source:

During the interwar years, Finnish officers were encouraged to visit other countries on exchange tours and take courses at officer academies in Europe, through this method the Finnish officer corps gained a wealth of different theories. It wasn’t uncommon for senior officers to allow their subordinates to test out ideas on maneuvers and writing of papers was highly encouraged. Using the German manual ‘Basic Rules for Conducting Positional Warfare’, Finland adopted a 4 layered defence in depth system on the Karelian Isthmus. This was then coupled with a delay strategy performed by Border Guard and Local Civil Guard units.

Lake Ladoga – The Dangerous flank

Unfortunately the main focus of Finland’s defensive plans had been upon the Isthmus, to the point that almost everywhere else was neglected. This was rectified when the then Lieutenant Colonel Paavo Talvela wrote a thesis on the ‘the offensive opportunities in Ladoga Karelia’, who then proved his thesis with several wargames throughout the 1930s. With this in mind, a plan for the possible Soviet thrust around the north of Lake Ladoga was planned for. Several defensive positions would be constructed, centered on Impilahti, which would stall a Soviet advance. It was believed that a Soviet force would be overconfident from an almost unopposed advance from the border and thus allow its lines of communication to be overstretched and undefended. Then small Finnish assault units would attack the columns from the supposedly impassable forests on the enemy’s right and rear flanks, with the lake on their left and a strong defensive line ahead of them, it was assumed that the attacking force would be annihilated.

The North Finland Group – The Wildlands

With the sparsely populated and developed parts of northern Finland, it was given less of a focus by military planning. This made sense as the area contained little in the way of roads, railways and other essential bits of infrastructure to support a military expedition. Thought this didn’t mean it was wholly neglected, military commanders realised that while the bulk of their own and the Soviet Union’s resources would be deployed around the Isthmus area, there would be fighting in the northern areas too. The only way for Finland to maintain any control of an advance into the north of the country would be through a strategy of active defence. By taking advantage of the poor road network and their learned ability to ski, small units of Finns could carry out large encirclement maneuvers against their Soviet counterparts. It was quickly revealed that the Red Army halted with every contact and that they didn’t use screening forces on their flanks. This led to the Finns developing what would become known to the world as Motti tactics.

The Navy – A Wasted Resource?

The Finnish Navy was split into two branches, the Fleet and Coast Artillery. After the smoke of the civil war clear, the newly independent Finland found itself with a fleet of some thirty Tsartist vessels of various conditions. After several incidents during the 1920s, a new law was passed which saw the Navy go through a large scale modernisation period. The new Finnish fleet would be centered around two coastal defence ships, Väinämöinen and Ilmarinen, and supported by several gun boats, torpedo boats and submarines. With these new vessels, the grand plan was for the fleet to be used in an anti-invasion role, using the numerous archipelagoes as cover and their shallow draught to travel where similarly sized vessels couldn’t go. Another role was to create a defensive network of mines, and for this reason most of the vessels of the Finnish Navy could lay mines.

Two Finnish submarines at port in the Åland Islands. Source: SA-Kuva

The main power of the Navy was in the coastal artillery. During the construction of the Main Defence Line, it was decided that each would be protected by large coastal artillery forts. These units were planned to secure both the Viipuri and Lake Ladoga areas from any attempts of invasion and could also be used as limited support to defensive operations on the Isthmus.

The Air Force – Defenders of the Skies

During the interwar period, the Finnish Air Force looked to the European nations for help in creating an effective air force. The international trend was for offensive policies and Finland followed along, planning on a mixture of fighter, bomber and dual reconnaisse/bomber aircraft. Due to the vast stretches of untamed forest, large number of lakes and small number of airfields, there was a favour for seaplanes. When Marshal Mannerheim was made Chairman of the Defence Committee in 1931, he ordered assessments to be conducted throughout the armed forces. As a result of the assessments, a programme of reorganisation and procurement was started. The emphasis for the air force was around fighters in a defensive role, supported by a handful of bombers and dual reconnaisse/bomber aircraft which were to be used to assist the army.

The Air Force was under no delusions that any air war with the Soviet Union would see the numbers be greatly against them and so tactics were developed to increase the defensive potential of the limited numbers of aircraft in their possession. Gunnery training was improved and each pilot was assigned an increasing amount of time in order to hone their skills. This was paired with recognition of the most vulnerable parts of an aircraft, which allowed for less ammunition used in bringing down a plane. The standard formation was changed from a tight three plane formation to a loose four, allowing for two pairs and thus increasing the firepower of a unit without sacrifice. Pilots were taught to use their initiative and a policy of “first see, first shoot” allowed the unit to react quickly during sorties. An offensive spirit was fostered within the fighter units which translated to increased surprise and initiative, as many large Soviet formations were taken by surprise by the sudden appearance of a handful of Finnish fighters.

Finland had 41 Fokker D.XXI’s when the Winter War broke out. By the end of the war, they had an impressive 16:1 exchange ratio despite their obsolete design. Source: SA-Kuva

The small number of bombers were to be used in an interdiction role. The Bristol Blenheim bombers were very fast and could be used to strike at supply lines and cause havoc for the logistics on an advancing army. They also had a secondary role as reconnaissance, thanks again to their speed, and during the Winter War this intelligence was invaluable to the Finnish defenders.

Anti-Aircraft defence was also under the purvey of the Air Force. While the military did recognise the need for effective anti-aircraft weapons, it would continually take a back seat to other procurements. The first AA battery wasn’t established until 1926 and the founding of more was a slow process. Despite this, the AA branch did work on several plans and on paper they had an effective integrated air defence plan. As the Isthmus was considered the most likely route for an invasion, the majority of the AA units would be deployed there in the rear areas of the army. They would form an umbrella of fire in order to keep the lines of communication, which were extremely vulnerable that close to the front, open. This didn’t mean that the home front was neglected and there were several batteries placed around towns and cities throughout the country. Even with the lack of numbers, small calibre and obsolescence of the majority of AA weaponry, they made up for it with a very well structured command and control and this achieved good results in either bringing down enemy aircraft or at least disrupting the formation.

A 40mm Bofors gun position ready in the rear area of the Army of the Isthmus. These light AA pieces helped to protect vital lines of communication. Source: SA-Kuva

How the plans worked when war came

It is said that no plan survives first contact with the enemy and this still rang true during the Winter War. Despite having mobilised the majority of their forces under the guise of ‘Extraordinary Maneuvers’ in October 1939 and having most units in their war time positions when the conflict started, not everything went smoothly.

The plan for a slow, delayed, scorched earth retreat on the Karelian Isthmus carried out by designated Suojajoukot (Protective Groups) didn’t turn out as planned. Lieutenant General Hugo Viktor Österman, commander of the Army of the Isthmus, has often been criticised for not being aggressive enough in those opening days and allowing the protective groups to pull back too quickly. This may be an unfair criticism and some have pointed out that with the overwhelming numbers of tanks, artillery and infantry, the small protective groups, lightly armed as they were, were unable to hold out longer than they did. It is worth pointing out that these protective groups did appear to start rallying and offering stiffer resistance a few days into the war, once the initial shock wore off and allowed for time to strengthen the main defence line.

Deployment of the Protective Groups and the rest of the Army of the Ishtmus at the outbreak of the war. Source: Wiki

Another failure occurred in the Lake Ladoga area, as expected the Soviets attempt a right sweeping advance and the 4th Corps was ready to enact the delay, halt and flank of the original plan. However, Major General Juho Heiskanen allowed several of his units to retreat, placing the entire defence of Lake Ladoga-Karelia area at risk. Marshal Mannerheim replaced the general on the 4th December with Major General Woldemar Hägglund, who managed to enact the original plans for the region to much greater effect than initially war gamed.

But it needs to be highlighted that even though the early days seemed to be a failure of the original plans laid out pre-war, they did achieve their overall goals. Finland knew from the onset that it would never be able to defeat a large nation like the USSR in a conventional total war, but it could delay and even stall an advance using a mixture of conventional and unconventional warfare. The desired outcome was that either the League of Nations, or one of the Great Powers, would come to their aid; or that they could cause enough damage through their tactics that it would force the USSR to the negotiating table. Another point to look at is that everyone, including Marshal Mannerheim, believed that no more than 12 Divisions, with the majority being deployed on the Isthmus, would be used in an operation against Finland. When war broke out, there was 12 Divisions deployed north of Lake Ladoga alone.

The war at sea had no effect on the outcome of the war but this was mainly because the sea froze by the end of December, making it impossible to conduct operations. Though the investment in coastal artillery positions did pay off though. Several artillery positions carried out their intended role of defending the coastal areas from possible invasions. The most well known being the clashes between the batteries at Fort Saarenpää and the Soviet vessels, Marat and Oktyabrskaya Revolutsiya.

The Air Force proved that the switch to a fighter based aggressive defensive force was the right call. Even though the Fokker D. XXIs were clumsy and slow, the Finns managed a 16:1 exchange ratio. Intelligence gathered by the air force allowed the artillery to accurately hit targets of importance and thus lessen the effectiveness of the Red Army. The dual reconnaissance/bomber squadrons suffered the greatest losses, their obsolete biplanes being unable to stand up to Soviet fighters and AA guns. This didn’t last long though and Air Force command did switch them to night interdiction missions. In this role they performed well in harassing the sleeping enemy, blowing up supply centers and cutting transportation routes.

In a later article I plan to look more indepth at the effectiveness of the Finnish Army. I also would like to touch upon certain tactics used by the Finnish military during the War. However this article should give a general overview of how the Finnish Army planned to fight.


Nikunen, Heikki. Air Defence in Northern Europe. (National Defence College Helsinki, 1997)
Sander, Gordon F. The Hundred Day Winter War: Finland’s Gallant Stand against the Soviet Army. (University Press of Kansas, 2013)
Van Dyke, Carl. The Soviet Invasion of Finland, 1939–40. (Routledge, 1997)
Tuunainen, Pasi. Finnish Military Effectiveness in the Winter War, 1939-1940 (Springer, 2016)
Grooss, Poul. The Naval War in the Baltic, 1939-1945. (Naval Institute Press,June 15, 2017)

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