|Partof:||World War II|
|Date:||30 November 1939 – 13 March 1940|
|Territory:||Cession of the Gulf of Finland islands, Karelian Isthmus, Ladoga Karelia, Salla, and Rybachy Peninsula, and rental of Hanko to the Soviet Union|
Finnish Democratic Republic (A puppet state. Recognized only by USSR.)
|Commander1:||Carl Gustaf Emil Mannerheim|
Otto Wille Kuusinen
|Strength1:||337,000–346,500 men  |
998,100 men (overall)2,514–6,541 tanks
|Casualties1:||25,904 dead or missing  |
957 civilians in air raids
70,000 total casualties
|Casualties2:||126,875 dead or missing |
188,671 wounded, injured or burned
3,543 tanks  
323,000 total casualties
The Winter War (Finnish: talvisota, Swedish: vinterkriget, Russian: link=no|''Зимняя война'' (trans. Zimnyaya voyna)) was a military conflict between the Soviet Union and Finland. It began with a Soviet offensive on 30 November 1939—two months after the start of World War II and the Soviet invasion of Poland—and ended on 13 March 1940 with the Moscow Peace Treaty. The League of Nations deemed the attack illegal and expelled the Soviet Union from the League on 14 December 1939.
The Soviet forces had more than three times as many soldiers as the Finns, thirty times as many aircraft, and a hundred times as many tanks. The Red Army, however, had been crippled by Soviet leader Joseph Stalin's Great Purge of 1937, reducing the army's morale and efficiency shortly before the outbreak of the fighting. With more than 30,000 of its army officers executed or imprisoned, including most of those of the highest ranks, the Red Army in 1939 had many inexperienced senior officers.  Because of these factors, and high commitment and morale in the Finnish forces, Finland was able to resist the Soviet invasion for far longer than the Soviets expected.
Hostilities ceased in March 1940 with the signing of the Moscow Peace Treaty. Finland ceded 11% of its pre-war territory and 30% of its economic assets to the Soviet Union. Soviet losses on the front were heavy, and the country's international reputation suffered. The Soviet forces did not accomplish their objective of the total conquest of Finland, but did gain substantial territory along Lake Ladoga, providing a buffer for Leningrad, and territory in Northern Finland. The Finns, however, retained their sovereignty and enhanced their international reputation.
The peace treaty thwarted the Franco-British plan to send troops to Finland through northern Scandinavia. One of the operation's major goals had been to take control of northern Sweden's iron ore and cut its deliveries to Germany.
See main article: Background of the Winter War.
Finland constituted the eastern part of the Kingdom of Sweden for centuries before 1809. At that time, to protect its imperial capital, Saint Petersburg, the Russians conquered Finland and converted it into an autonomous buffer state within the Russian Empire. Finland enjoyed wide autonomy until the end of the 19th century, when Russia began attempts to assimilate Finland as part of a general policy to strengthen the central government and unify the Empire through Russification. While abortive because of Russia's internal strife, these attempts ruined Russia's relations with the Finns and increased support for Finnish self-determination movements.
The outbreak of the First World War and the collapse of the Russian Empire gave Finland a window of opportunity; on 6 December 1917, the Senate of Finland declared the country's independence. The new Bolshevik Russian government was weak, and with the threat of civil war looming Soviet Russia recognized the new Finnish government just three weeks after the declaration of independence. Sovereignty was fully achieved in May 1918 after a short civil war and the expulsion of Bolshevik troops.
Finland joined the League of Nations in 1920. Finland sought security guarantees from the League, but its primary goal was cooperation with the Scandinavian countries. The Finnish and Swedish militaries engaged in wide-ranging cooperation, but were more focused on the exchange of information and defence planning for the Åland islands than on military exercises, or the stockpiling and deployment of materiel. Nevertheless, the government of Sweden carefully avoided committing itself to Finnish foreign policy. Another Finnish military policy was the top secret military cooperation between Finland and Estonia.
The 1920s and early 1930s were a politically unstable time in Finland. The Communist Party of Finland was declared illegal in 1931, and the Lapua Movement organised anti-communist violence, which culminated in a failed uprising in 1932. Thereafter the ultra-nationalist Patriotic People's Movement (IKL) had a minor presence – at most 14 seats out of 200 in the Finnish parliament. By the late 1930s, the export-oriented Finnish economy was growing and the country had almost solved its problems with extreme political movements.
After the Soviet involvement in the Finnish Civil War in 1918, no formal peace treaty was signed. In 1918 and 1919, Finnish volunteer forces conducted two unsuccessful military incursions across the Russian border: the Viena and Aunus expeditions. In 1920, Finnish communists based in Soviet Russia attempted to assassinate the former Finnish White Guards Commander-in-Chief General CGE Mannerheim. On 14 October 1920, Finland and Soviet Russia signed the Treaty of Tartu, confirming the new Finnish–Soviet border as the old border between the autonomous Grand Duchy of Finland and Imperial Russia proper. In addition, Finland received Petsamo, with its ice-free harbour on the Arctic Ocean. Despite the signing of the treaty, relations between the two countries remained strained. The Finnish government allowed volunteers to cross the border to support the East Karelian Uprising in 1921, and Finnish communists in the Soviet Union continued to prepare for a revanche and staged a cross-border raid into Finland, called the "Pork mutiny", in 1922.
In 1932, the Soviet Union signed a non-aggression pact with Finland, which was reaffirmed for a 10-year period in 1934. However, relations between the two countries remained largely de minimis. While foreign trade in Finland was booming, less than 1% of Finnish trade was with the Soviet Union. In 1934, the Soviet Union joined the League of Nations.
During the Stalin era, Soviet propaganda painted Finland's leadership as a "vicious and reactionary Fascist clique." Marshal C.G.E. Mannerheim and Väinö Tanner, the leader of the Finnish Social Democratic Party, were targeted for particular scorn. With Joseph Stalin gaining near-absolute power through the Great Purge of 1938, the Soviet Union changed its foreign policy toward Finland in the late 1930s. The Soviet Union began pursuing the reconquest of the provinces of Tsarist Russia lost during the chaos of the October Revolution and the Russian Civil War. The Soviet leadership believed that the old empire had ideal security and territorial possessions, and wanted the newly christened city of Leningrad to enjoy a similar security.
In April 1938, an NKVD agent, Boris Yartsev contacted the Finnish foreign minister Rudolf Holsti and Prime Minister Aimo Cajander, stating that the Soviet Union did not trust Germany and that war was considered possible between the two countries. The Red Army would not wait passively behind the border but would rather "advance to meet the enemy." Finnish representatives assured Yartsev that Finland was committed to a policy of neutrality and that the country would resist any armed incursion. Yartsev suggested that Finland cede or lease some islands in the Gulf of Finland along the seaward approaches to Leningrad. Finland refused. 
Negotiations continued throughout 1938 without results. Finnish reception of Soviet entreaties was decidedly cool, as the violent collectivisation and purges in Stalin's Soviet Union resulted in a poor opinion of the country. In addition, most of the Finnish communist elite in the Soviet Union had been executed during the Great Purge, further tarnishing the Soviet Union's image in Finland. At the same time, Finland was trying to negotiate a military co-operation plan with Sweden, hoping for a joint defence of the Åland Islands.
The Soviet Union and Nazi Germany signed the Molotov–Ribbentrop Pact in August 1939. The pact was nominally a non-aggression treaty, but it included a secret protocol in which the Eastern European countries were divided into spheres of interest. Finland fell into the Soviet sphere. On 1 September 1939, Germany began its invasion of Poland and two days later Great Britain and France declared war against Germany. Shortly afterwards, the Soviets invaded eastern Poland. The Baltic states were later forced to accept treaties allowing the Soviets to establish military bases and to station troops on their soil. The government of Estonia accepted the ultimatum, signing the corresponding agreement in September. Latvia and Lithuania followed in October. Unlike the Baltic states, Finland started a gradual mobilisation under the guise of "additional refresher training."
The Soviets had already started an intensive mobilisation near the Finnish border in 1938–1939. However, assault troops necessary for invasion did not begin deployment until October 1939. Operational plans made in September called for the invasion to start in November. 
On 5 October 1939, the Soviet Union invited a Finnish delegation to Moscow for negotiations. J.K. Paasikivi, the Finnish ambassador to Sweden, was sent to Moscow to represent the Finnish government. The Soviets demanded that the border between the USSR and Finland on the Karelian Isthmus be moved westward to a point only 30km east of Viipuri and that the Finns destroy all existing fortifications on the Karelian Isthmus. They also demanded the cession of islands in the Gulf of Finland as well as the Kalastajansaarento peninsula. Furthermore, the Finns would have to lease the Hanko Peninsula for 30 years and permit the Soviets to establish a military base there. In exchange, the Soviet Union would cede two municipalities with twice the territory demanded from Finland.  Accepting Soviet demands would have forced the Finns to dismantle their defences in Finnish Karelia.
The Soviet offer divided the Finnish government, but it was eventually rejected. On 31 October, in the assembly of the Supreme Soviet, Molotov announced Soviet demands in public. The Finns made two counteroffers whereby Finland would cede the Terijoki area to the Soviet Union, which would double the distance between Leningrad and Finnish border, far less than the Soviets had demanded. From the Soviet point of view the negotiations were finished.
On 26 November, a border incident was reported near the village of Mainila. A Soviet border guard post had been shelled by an unknown party resulting, according to Soviet reports, in the deaths of four and injuries of nine border guards. Research conducted by several Finnish and Russian historians later concluded that the shelling was carried out from the Soviet side of the border by an NKVD unit with the purpose of providing the Soviet Union with a casus belli and a pretext to withdraw from the non-aggression pact.
Soviet Foreign Minister Vyacheslav Molotov claimed it was a Finnish artillery attack and demanded that Finland apologise for the incident and move its forces beyond a line 20- away from the border. Finland denied responsibility for the attack, rejected the demands, and called for a joint Finnish–Soviet commission to examine the incident. The Soviet Union then claimed that the Finnish response was hostile and renounced the non-aggression pact on 28 November. In the following years, Soviet historiography described the incident as a Finnish provocation. Doubt on the official Soviet version was cast only in the late 1980s, in the times of glasnost. However, the issue continued to divide Russian historiography even after the collapse of the Soviet Union. 
On 30 November, Soviet forces invaded Finland with 21 divisions, totaling some 450,000 men, and bombed Helsinki.  Later the Finnish statesman J. K. Paasikivi commented that the Soviet attack without a declaration of war violated three different non-aggression pacts: the Treaty of Tartu signed in 1920, the non-aggression pact between Finland and the Soviet Union signed in 1932 and again in 1934, and also the Covenant of the League of Nations, which the Soviet Union signed in 1934. C.G.E. Mannerheim was appointed Commander-in-Chief of the Finnish Defence Forces after the Soviet attack. In further reshuffling, the Finnish government named Risto Ryti as the new prime minister and Väinö Tanner as foreign minister.
On 1 December, the Soviet Union formed a puppet government intended to rule Finland after the Red Army conquered it. Called the Finnish Democratic Republic, it was headed by O. W. Kuusinen. The government was also called "The Terijoki Government", named after the village of Terijoki, the first place captured by the advancing Soviet army. After the war the puppet government was disbanded. From the very outset of the war, working-class Finns stood behind the legal government in Helsinki. Finnish national unity against the Soviet invasion was later called the spirit of the Winter War.
At the start of the Winter War, Finland brought up the matter of the Soviet invasion before the League of Nations. The League expelled the Soviet Union on 14 December and exhorted its members to aid Finland.
At the beginning of the war, total victory over Finland was expected within a few weeks. The Red Army had just finished the invasion of eastern Poland at a cost of less than 1,000 casualties. Stalin's expectations of a quick Soviet triumph were backed up by the politician Andrei Zhdanov and military strategist Kliment Voroshilov, but other generals had their doubts. The chief of staff of the Red Army, Boris Shaposhnikov, advocated a serious buildup, extensive logistical and fire support preparations, and a rational order of battle, deploying the army's best units. Zhdanov's military commander Kirill Meretskov reported at the start of the hostilities: "The terrain of coming operations is split by lakes, rivers, swamps, and is almost entirely covered by forests... The proper use of our forces will be difficult." However, these doubts were not reflected in his troop deployments. Meretskov announced publicly that the Finnish campaign would take at the most two weeks. Soviet soldiers had even been warned not to cross the border into Sweden by mistake.
Stalin's purges devastated the officer corps of the Red Army; those purged included three of its five marshals, 220 of its 264 division-level commanders or higher, and 36,761 officers of all ranks. Fewer than half of the officers remained in total. They were commonly replaced by soldiers who were less competent but more loyal to their superiors. Furthermore, unit commanders were superseded by a political commissar, who ratified military decisions on their political merits, further complicating the Soviet chain of command. This system of dual command destroyed the independence of commanding officers.
Soviet generals were impressed by the success of the German blitzkrieg tactics. However, the blitzkrieg had been tailored to central European conditions with a dense, well-mapped network of paved roads. Armies fighting in central Europe had recognised supply and communications centres, which could be easily targeted by armoured vehicle regiments. Finnish army centres, by contrast, were deep inside the country. There were no paved roads, and even gravel or dirt roads were scarce; most of the terrain consisted of trackless forests and swamps. Waging a blitzkrieg in Finland was a highly difficult proposition, and the Red Army failed to meet the level of tactical coordination and local initiative required to execute blitzkrieg tactics in the Finnish theatre.
The Soviet forces were positioned as follows:
The Finnish strategy was dictated by geography. The frontier with the Soviet Union was more than 1000km long but was mostly impassable except along a handful of unpaved roads. In pre-war calculations, the Finnish General Staff, which had established its wartime headquarters at Mikkeli, estimated seven Soviet divisions on the Isthmus and no more than five along the whole border north of Lake Ladoga. In that case, the manpower ratio would favour the attacker by a ratio of 3:1. The true ratio was much higher; for example, 12 Soviet divisions were deployed to the north of Lake Ladoga.
An even greater problem than lack of soldiers was the lack of materiel; foreign shipments of antitank weapons and aircraft were arriving in small quantities. The ammunition situation was alarming, as stockpiles had cartridges, shells and fuel only for 19–60 days. The ammunition shortage meant the Finns could seldom afford counterbattery or saturation fire. Finnish tank forces were operationally non-existent.
The Finnish forces were positioned as follows:
|Tanks||T-26 tank, T-28, Kliment Voroshilov tank, BT tank (BT-2 and BT-5 mainly), T-37A tank, T-38 tank and various experimental and prototype fighting vehicles (such as SMK tank)||Vickers-Armstrong 6 ton tank, Renault F.T. Modèle 1917 (used only as dug-in bunkers)|
|Artillery and anti-tank||50mm, 82mm and 120mm mortars, artillery of various calibres ranging from 76mm light field cannons to the super heavy 203mm howitzer||Finnish Tampella 81mm mortars, 82 and 120mm mortars (captured from Soviet stocks), 76 K/02, also known as 76mm cannon model 1902, 37 PstK/36 anti-tank gun, Lahti anti-tank rifle model 1939, 20mm Madsen cannon (converted for anti-tank use)|
|Aircraft||Polikarpov I-15, Polikarpov I-153 "Chaika", Polikarpov I-16, Polikarpov R-5, Tupolev SB, Ilyushin DB-3, Tupolev TB-3||Fokker D.XXI, Bristol Bulldog (MK IV), Gloster Gladiator, Fiat G.50 "Freccia", Morane-Saulnier M.S.406, Fokker C.V, Fokker C.X, Blackburn Ripon, Junkers K 43, Bristol Blenheim Models I,IV, Hawker Hart|
|Small Arms and grenades||Mosin Nagant Model 1891/1930 bolt action rifle, variants included sniper and carbine versions. SVT38 semi automatic rifle, Maxim 1910 belt fed machine gun, DP-27 machine gun, TT33 semi-automatic pistol, Nagant M1895 revolver, F1 pineapple grenade, RGD-33 stick grenade||Mosin Nagant Model 1891 rifle (captured 1891/1930 rifles as well as locally produced and improved Finnish models of the basic Model 1891 (Models m1891-24, m/27, m/28 and m/28-30)), SVT38 (captured from Soviet stocks), Swedish Mauser rifle, Carcano 91/38 rifle (in 7.35 calibre), Suomi KP/-31 submachine gun, LS-26 light machine gun, DP-27 (captured from Soviet stocks). Luger pistol, Lahti L-35 pistol, TT33 semi-automatic pistol, Nagant M1895 revolver (the latter two pistol types were captured from Soviet stocks), Maxim 1910 Russian as well as Finnish variants including version 09/21, Satchel charges, Molotov cocktails, Finnish M32 stick grenade, Finnish M32 multi purpose grenade, Soviet RGD-33 stick grenade|
The Mannerheim Line, an array of Finnish defence structures, was located on the Karelian Isthmus about 30to from the Soviet border. The Red Army soldiers on the Isthmus numbered 250,000 facing 130,000 Finns. The Finnish command deployed a covering force of about 21,000 men in the area in front of the Mannerheim Line in order to delay and damage the Red Army before it reached the line.
In combat, the biggest cause of confusion among Finnish soldiers were Soviet tanks. The Finns had few anti-tank weapons and insufficient training in modern anti-tank tactics. However, the favoured Soviet armoured tactic was a simple frontal charge, the weaknesses of which could be exploited. The Finns learned that at close range, tanks could be dealt with in many ways; for example, logs and crowbars jammed into the bogie wheels would often immobilise a tank. Soon, Finns fielded a better ad hoc weapon, the Molotov Cocktail. It was a glass bottle filled with flammable liquids, with a simple hand-lit fuse. Molotov cocktails were eventually mass-produced by the Finnish Alko corporation and bundled with matches with which to light them. Eighty Soviet tanks were destroyed in the border-zone fighting.
By 6 December, all the Finnish covering forces had withdrawn to the Mannerheim Line. The Red Army began its first major attack against the Line in Taipale – the area between the shore of Lake Ladoga, the Taipale river and the Suvanto waterway. Along the Suvanto sector, the Finns had a slight advantage of elevation and dry ground to dig into. The Finnish artillery had scouted the area and made fire plans in advance, anticipating a Soviet assault. The Battle of Taipale began with a forty-hour Soviet artillery preparation. After the barrage, the Soviet infantry attacked across open ground but was repulsed with heavy casualties. From 6–12 December, the Red Army continued trying to engage using only one division. The Red Army next strengthened its artillery and brought tanks and the 10th Rifle Division to the Taipale front. On 14 December, the bolstered Soviet forces launched a new attack but were pushed back again. A third Soviet division entered the fight but performed poorly and panicked under shell fire. The assaults continued without success, and the Red Army suffered heavy losses. One typical Soviet attack during the battle lasted just an hour but left 1,000 dead and 27 tanks strewn on the ice.
North of Lake Ladoga, on the Ladoga Karelia front, the defending Finnish units relied on the terrain. Ladoga Karelia, as a large forest wilderness, did not have road networks for the modern Red Army. However, the Soviet 8th Army had extended a new railroad line to the border, which could double the supply capability on the front. But on 12 December, the advancing Soviet 139th Rifle Division, supported by the 56th Rifle Division, was defeated by a much smaller Finnish force under Paavo Talvela in the Tolvajärvi, the first Finnish victory of the war.
In central and northern Finland, roads were few and the terrain hostile. The Finns did not expect large-scale Soviet attacks, but the Soviets sent eight divisions, heavily supported by armour and artillery. The 155th Rifle Division attacked at Lieksa, and further north the 44th attacked at Kuhmo. The 163rd Rifle Division was deployed at Suomussalmi and charged with cutting Finland in half by marching the Raate Road. In Finnish Lapland, the Soviet 88th and 122nd Rifle Divisions attacked at Salla. The Arctic port of Petsamo was attacked by the 104th Mountain Rifle Division by sea and land, supported by naval gunfire.
The winter of 1939–1940 was exceptionally cold. One location on the Karelian Isthmus experienced a record low temperature of -43°C on 16 January 1940. At the beginning of the war, only those Finnish soldiers who were in active service had uniforms and weapons. The rest had to make do with their own clothing, which for many soldiers was their normal winter clothing with semblance of an insignia added. Finnish soldiers were skilled in cross-country skiing.
The cold, the snow, the forest, and the long hours of darkness were factors that the Finns could turn to their advantage. The Finns dressed in layers, and the ski troopers wore a lightweight white snow cape. This snow-camouflage made the ski troopers almost invisible as the Finns executed guerrilla attacks against Soviet columns. At the beginning of the war, Soviet tanks were painted in standard olive drab and men dressed in regular khaki uniforms. Not until late January 1940 did the Soviets paint their equipment white and issue snowsuits to their infantry.
Most Soviet soldiers had proper winter clothes, but this was not the case with every unit. In the battle of Suomussalmi, many Soviet soldiers died of frostbite. The Soviet troops lacked skill in skiing, so soldiers were restricted to movement by road and were forced to move in long columns. Furthermore, the Red Army lacked proper winter tents, and men had to sleep in improvised shelters. Some Soviet units had frostbite casualties as high as 10% even before crossing the Finnish border. The cold weather did confer one advantage: Soviet tanks were able to move more easily over frozen terrain and bodies of water, rather than being immobilised in swamps and mud.
In battles from Ladoga Karelia all the way north to the Arctic port of Petsamo, the Finns used guerrilla tactics. The Red Army was superior in numbers and materiel, but the Finns used the advantages of speed, tactics, and economy of force. Particularly on the Ladoga Karelia front and during the battle of Raate road, the Finns isolated smaller portions of numerically superior Soviet forces. With Soviet forces divided into smaller pieces, the Finns could deal with them individually and attack from all sides.
For many of the encircled Soviet troops in a pocket, (motti in Finnish), just staying alive was an ordeal comparable to combat. The men were freezing and starving and endured poor sanitary conditions. Historian William R. Trotter describes these conditions thus: "The Soviet soldier had no choice. If he refused to fight, he would be shot. If he tried to sneak through the forest, he would freeze to death. And surrender was no option for him; Soviet propaganda had told him how the Finns would torture prisoners to death."
The terrain on the Karelian Isthmus did not allow the exercise of guerilla tactics, so the Finns were forced to resort to the more conventional Mannerheim Line, with its flanks protected by large bodies of water. Soviet propaganda claimed that it was as strong as or even stronger than the Maginot Line. Finnish historians, for their part, have belittled the line's strength, insisting that it was mostly conventional trenches and log-covered dugouts.
The Finns had built 221 strongpoints along the Karelian Isthmus, mostly in the early 1920s. Many were extended in the late 1930s. Despite these defensive preparations, even the most fortified section of the Mannerheim Line had only one reinforced concrete bunker per kilometre. Overall, the line was weaker than similar lines in mainland Europe. According to the Finns, the real strength of the line were the "stubborn defenders with a lot of sisu" – a Finnish idiom roughly translated as "guts."
On the eastern side of the isthmus, the Red Army attempted to break through the Mannerheim Line in the battle of Taipale. On the western side, Soviet units faced the Finnish line at Summa, near the city of Viipuri, on 16 December. The Finns had built 41 reinforced concrete bunkers in the Summa area, making the defensive line in this area stronger than anywhere else on the Karelian Isthmus. However, because of a mistake in planning, the nearby Munasuo swamp had a 1km-wide gap in the line. During the first battle of Summa, a number of Soviet tanks broke through the thin line on 19 December, but the Soviets could not benefit from the situation because of insufficient cooperation between branches of service. The Finns remained in their trenches, allowing the Soviet tanks to move freely behind the Finnish line, as the Finns had no proper anti-tank weapons. However, the Finns succeeded in repelling the main Soviet assault. The tanks, stranded behind enemy lines, attacked the strongpoints at random until they were eventually destroyed, 20 in all. By 22 December, the battle ended in a Finnish victory.
The Soviet advance was stopped at the Mannerheim Line. Red Army troops suffered from poor morale and a shortage of supplies, eventually refusing to participate in more suicidal frontal attacks. The Finns, led by General Harald Öhquist, decided to launch a counterattack and encircle three Soviet divisions into a motti near Viipuri on 23 December. Öhquist's plan was bold, but it failed. The Finns lost 1,300 men, and the Soviets were later estimated to have lost a similar number.
The strength of the Red Army north of Lake Ladoga (in Ladoga Karelia) surprised the Finnish General Staff. Two Finnish divisions were deployed there: the 12th Division led by Lauri Tiainen and the 13th Division led by Hannu Hannuksela. They also had a support group of three brigades, bringing their total strength to over 30,000. The Soviets deployed a division for almost every road leading west to the Finnish border. The Eighth Army was led by Ivan Khabarov, who was replaced by Grigori Shtern on 13 December. The Soviets' mission was to destroy the Finnish troops in the area of Ladoga Karelia and advance into the area between Sortavala and Joensuu within 10 days. The Soviets had a 3:1 advantage in manpower and 5:1 advantage in artillery as well as air supremacy.
Finnish forces panicked and retreated in front of the overwhelming Red Army. The commander of the Finnish IV Army Corps was replaced by Woldemar Hägglund on 4 December. On 7 December, in the middle of the Ladoga Karelian front, Finnish units retreated near the small stream of Kollaa. The waterway itself did not offer protection, but alongside there were ridges up to 10m (30feet) high. The battle of Kollaa lasted until the end of the war. A memorable quote, "Kollaa holds" (Finnish: Kollaa kestää) became a legendary motto among the Finns. Further contributing to the legend of Kollaa was the sniper Simo Häyhä, dubbed "the White Death" by Soviets, who served in the Kollaa front. To the north, the Finns retreated from Ägläjärvi to Tolvajärvi on 5 December and then repelled a Soviet offensive in the battle of Tolvajärvi on 11 December.
In the south, two Soviet divisions were united on the northern side of the Lake Ladoga coastal road. As before, these divisions were trapped as the more mobile Finnish units were able to counterattack from the north to flank the Soviet columns. On 19 December, the Finns temporarily ceased their assaults, as the soldiers were exhausted. It was not until the period 6–16 January 1940 that the Finns went on the offensive again, cutting Soviet division into smaller groups of different-sized mottis.
Contrary to Finnish expectations, the encircled Soviet divisions did not try to break through to the east but instead entrenched. They were expecting reinforcements and supplies to arrive by air. As the Finns lacked the necessary heavy artillery equipment and were short of men, they often did not directly attack mottis they had created; instead, they focused on eliminating only the most dangerous threats. Often the motti tactic was not part of pre-planned doctrine but a Finnish adaptation to the behaviour of Soviet troops under fire.
In spite of the cold and hunger, the Soviet troops did not surrender easily but fought bravely, often entrenching their tanks to be used as pillboxes and building timber dugouts. Some specialist Finnish soldiers were called in to attack the mottis; the most famous of them was Major Matti Aarnio, or "Motti-Matti," as he became known.
In northern Karelia, Soviet forces were outmanoeuvred at Ilomantsi and Lieksa. The Finns used effective guerrilla tactics, taking special advantage of superior skiing skills and snow-white layered clothing and executing many surprise ambushes and raids. By the end of December, the Soviets decided to retreat and transfer resources to more critical fronts.
The Suomussalmi–Raate was a double operation, which would later be used by military academics as a classic example of what well-led troops and innovative tactics can do against a much larger adversary. Suomussalmi was a small provincial town of 4,000. The area has long lakes, many wild forests and few roads. The Finnish command believed that the Soviets would not attack here, but the Red Army committed two divisions to the area with orders to cross the wilderness, capture the city of Oulu and effectively cut Finland in two. There were two roads leading to Suomussalmi from the frontier: the northern Juntusranta road and the southern Raate road.
The battle of Raate road, which occurred during the month-long battle of Suomussalmi, resulted in one of the largest losses in the Winter War. The Soviet 44th and parts of the 163rd Rifle Divisions, comprising about 14,000 troops, were almost completely destroyed by a Finnish ambush as they marched along the forest road. A small unit blocked the Soviet advance while Finnish Colonel Hjalmar Siilasvuo and his 9th Division cut off the retreat route, split the enemy force into smaller fragments, and then proceeded to destroy the remnants in detail as they retreated. The Soviets suffered 7,000–9,000 casualties, while the Finnish units lost only 400 men. In addition, the Finnish troops captured dozens of tanks, artillery pieces, anti-tank guns, hundreds of trucks, almost 2,000 horses, thousands of rifles, and much-needed ammunition and medical supplies.
In Finnish Lapland, the forests gradually thin out until in the north there are no trees at all. Thus, the area offers more room for tank deployment, but it is vastly underpopulated and experiences copious snowfall. The Finns expected nothing more than raiding parties and reconnaissance patrols, but instead the Soviets sent full divisions. On 11 December, the Finns rearranged the defence of Lapland and detached the Lapland Group from the North Finland Group. The group was placed under the command of Kurt Wallenius.
In southern Lapland, near the tiny rural village of Salla, the Soviet force advanced with two divisions, the 88th and 112th, totalling 35,000 men. In the battle of Salla the Soviets advanced easily to Salla, where the road forked. The northern branch moved toward Pelkosenniemi while the rest pushed on toward Kemijärvi. On 17 December, the Soviet northern group, comprising an infantry regiment, a battalion, and a company of tanks, was outflanked by a Finnish battalion. The 112th retreated, leaving much of its heavy equipment and vehicles behind. Following this success, the Finns shuttled reinforcements down to the defensive line in front of Kemijärvi. The Soviets hammered the defensive line without success. The Finns counterattacked, and the Soviets were pushed back to a new defensive line where they stayed for the rest of the war. 
To the north was Finland's only ice-free port in the Arctic, Petsamo. The Finns did not have the manpower to defend it fully as the main front was down the Karelian Isthmus. In the battle of Petsamo, the Soviet 104th division attacked the Finnish 104th Independent Cover Company. The Finns gave up Petsamo easily and concentrated on delaying actions. The area was treeless, windy and relatively low, offering little defensible terrain. However, during the winter, the Finns in Lapland had the advantage of almost constant darkness and extreme temperatures. The Finns executed guerrilla attacks against Soviet supply lines and patrols. As a result, the Soviet movements were halted by the efforts of one-fifth as many Finns.
Joseph Stalin was not pleased with the results of the first month of the Finnish campaign. The Red Army had been humiliated. By the third week of the war, Soviet propaganda was working hard to explain the failures of the Soviet army to the populace: blaming bad terrain and harsh climate, and falsely claiming that the Mannerheim Line was stronger than the Maginot Line, and that the Americans had sent 1,000 of their best pilots to Finland. Chief of Staff Boris Shaposhnikov was given full authority over operations in the Finnish theatre, and he ordered the suspension of frontal assaults in late December. Kliment Voroshilov was replaced with Semyon Timoshenko as the commander of the Soviet forces in the war on 7 January.
The main focus of the Soviet attack was switched to the Karelian Isthmus. Timoshenko and Zhdanov reorganised and tightened control between different branches of service in the Red Army. They also changed tactical doctrines to meet the realities of the situation. All Soviet forces on the Karelian Isthmus were divided into two armies: the 7th and the 13th Armies. The 7th Army, now under Kirill Meretskov, would concentrate 75% of its strength against the 16km stretch of the Mannerheim Line between Taipale and the Munasuo swamp. Tactics would be basic: an armoured wedge for the initial breakthrough, followed by the main infantry and vehicle assault force. The Red Army would prepare by pinpointing the Finnish frontline fortifications. The 123rd Assault Division then rehearsed the assault on life-size mockups. The Soviets shipped massive numbers of new tanks and artillery pieces to the theatre. Troops were increased from ten divisions to 25–26 divisions, six or seven tank brigades and several independent tank platoons, totalling 600,000 men. On 1 February, the Red Army began a massive offensive, firing 300,000 shells into the Finnish line in the first 24 hours of the bombardment.
Although the Karelian Isthmus front was less active in January than in December, the Soviets began increasing bombardments, wearing down the defenders and softening their fortifications. During daylight hours, the Finns took shelter inside their fortifications from the bombardments and repaired damage during the night. The situation led quickly to war exhaustion among the Finns, who lost over 3,000 men in trench warfare. The Soviets also made occasional small infantry assaults with one or two companies. Because of the shortage of ammunition, Finnish artillery emplacements were under orders to fire only against directly threatening ground attacks. On 1 February, the Soviets further escalated their artillery and air bombardments.
Although the Soviets refined their tactics and morale improved, the generals were still willing to accept massive losses in order to reach their objectives. Attacks were screened by smoke, heavy artillery and armour support, but the infantry charged in the open and in dense formations. Unlike their tactics in December, Soviet tanks advanced in smaller numbers. The Finns could not easily eliminate tanks if infantry troops protected them. After 10 days of round-the-clock artillery barrages, the Soviets achieved a breakthrough on the western Karelian Isthmus in the second battle of Summa.
On 11 February, the Soviets had about 460,000 men, over 3,350 artillery pieces, about 3,000 tanks and about 1,300 aircraft deployed on the Karelian Isthmus. The Red Army was constantly receiving new recruits after the breakthrough. Opposing them the Finns had eight divisions, totalling about 150,000 men. One by one, the defenders' strongholds crumbled under the Soviet attacks and the Finns were forced to retreat. On 15 February, Mannerheim authorised a general retreat of the Second Corps to the Intermediate Line. On the eastern side of the isthmus, the Finns continued to resist Soviet assaults, repelling them in the battle of Taipale.
Although the Finns attempted to re-open negotiations with Moscow by every means during the war, the Soviets did not respond. In early January, Finnish communist and feminist playwright Hella Wuolijoki contacted the Finnish government. She offered to contact Moscow through the Soviet Union's ambassador to Sweden, Alexandra Kollontai. Wuolijoki departed for Stockholm and met Kollontai secretly at a hotel. Soon Molotov decided to extend recognition to the Ryti–Tanner government as the legal government of Finland and put an end to the puppet Terijoki Government of Kuusinen that the Soviets had set up.
By mid-February, it became clear that the Finnish forces were rapidly approaching exhaustion. For the Soviets, casualties were high, the situation was a source of political embarrassment of the Soviet regime, and there was a risk of Franco-British intervention. Furthermore, with the spring thaw approaching, the Soviet forces risked becoming bogged down in the forests. The Finnish foreign minister Väinö Tanner arrived in Stockholm on 12 February and negotiated the peace terms with the Soviets through the Swedes. German representatives, not aware that the negotiations were underway, suggested on 17 February that Finland negotiate with the Soviet Union.
Both Germany and Sweden were keen to see an end to the Winter War. The Germans feared losing iron ore fields in northern Sweden and threatened to attack at once if the Swedes granted the Allied forces right of passage. The Germans even had a theoretical invasion plan called the Studie Nord against Scandinavian countries, which later became the full-blown Operation Weserübung. As the Finnish Cabinet hesitated in the face of the harsh Soviet conditions, Sweden's King Gustav V made a public statement on 19 February in which he confirmed having declined Finnish pleas for support from Swedish troops. On 25 February, the Soviet peace terms were spelled out in detail. On 29 February, the Finnish government accepted the Soviet terms in principle and was willing to enter into negotiations.
On 5 March, the Red Army advanced 10to past the Mannerheim Line and entered the suburbs of Viipuri. That same day, the Red Army established a beachhead on the western Gulf of Viipuri. The Finns proposed an armistice on that day, but the Soviets, wanting to keep the pressure on the Finnish government, declined the offer the next day. The Finnish peace delegation went to Moscow via Stockholm and arrived on 7 March. The Soviets made further demands as their military position was strong and improving. On 9 March, the Finnish military situation on the Karelian Isthmus was dire as troops were experiencing heavy casualties. In addition, artillery ammunition supplies were exhausted and weapons were wearing out. The Finnish government, noting that the hoped-for Franco-British military expedition would not arrive in time, as Norway and Sweden had not given the right of Allied passage, had little choice but to accept the Soviet terms. The formal peace treaty was signed in Moscow on 12 March. A cease-fire took effect the next day at noon Leningrad time, 11 a.m. Helsinki time.
See main article: Aerial warfare in the Winter War.
The Soviet Union enjoyed air supremacy throughout the war. The Soviet Air Force, supporting the Red Army's invasion with about 2,500 aircraft (the most common of which was the Tupolev SB) was not as effective as the Soviets might have hoped. The material damage by the bomb raids was slight as Finland did not offer many valuable targets for strategic bombing. Very often, targets were small village depots with little value. The country had only a few modern highways in the interior, therefore making railway systems the main targets for bombers. The rail tracks were cut thousands of times, but they were easy to repair and Finns usually had trains running again in a matter of hours. The Soviet air force learned from its early mistakes, and by late February they instituted more effective tactics.
The largest bombing raid against the capital of Finland, Helsinki, occurred on the first day of the war. The capital was bombed only a few times thereafter. All in all, Finland lost only 5% of total man-hour production time because of Soviet bombings. Nevertheless, Soviet air attacks affected thousands of civilians, killing 957, as the Soviets recorded 2,075 bombing attacks in 516 localities. The city of Viipuri, a major Soviet objective close to the Karelian Isthmus front, was almost levelled by nearly 12,000 bombs. No attacks on civilian targets were mentioned in Soviet radio or newspaper reports. In January 1940, the Pravda continued to stress that no civilian targets in Finland had been struck, even by accident.
At the beginning of the war, Finland had a very small air force, with only 114 combat planes fit for duty. Missions were very limited, and fighter aircraft were mainly used to repel Soviet bombers. Strategic bombings could also double as opportunities for military reconnaissance. Old-fashioned and few in number, aircraft could not offer support for Finnish ground troops. In spite of losses, the number of planes in the Finnish Air Force had risen by over 50% by the end of the war. The Finns received shipments of British, French, Italian, Swedish and American aircraft.
Finnish fighter pilots would often fly their motley collection of planes into Soviet formations that outnumbered them 10 or even 20 times. Finnish fighters shot down a confirmed 200 Soviet aircraft, losing 62 of their own. In addition, Finnish anti-aircraft brought down more than 300 enemy aircraft. Many times, a Finnish forward air base consisted of a frozen lake, a windsock, a telephone set and some tents. Air-raid warnings were given by Finnish women organised by the Lotta Svärd. In addition to combat, it is estimated that the Soviet air force lost about 400 aircraft because of inclement weather, lack of fuel and tools, and during transportation to the front. The Soviet Air Force flew approximately 44,000 sorties during the war.
See main article: Naval warfare in the Winter War.
Naval activity during the Winter War was low. The Baltic Sea began to freeze over by the end of December, which made the movement of warships very difficult; by mid-winter, only ice breakers and submarines could still move. The other reason for low naval activity was the nature of Soviet Navy forces in the area. The Baltic Fleet was a coastal defence force which did not have the training, logistical structure, or landing craft to undertake large-scale operations. The Baltic Fleet possessed two battleships, one heavy cruiser, almost 20 destroyers, 50 motor torpedo boats, 52 submarines, and other miscellaneous vessels. The Soviets used naval bases in Paldiski, Tallinn and Liepāja for their operations.
The Finnish Navy was a coastal defence force with two coastal defence ships, five submarines, four gunboats, seven motor torpedo boats, one minelayer and six minesweepers. The two coastal defence ships, and, were moved to the harbour in Turku where they were used to bolster the air defences. Their anti-aircraft guns shot down one or two planes over the city, and the ships remained there for the rest of the war. In addition to its role in coastal defence, the Finnish Navy protected the Åland islands and Finnish merchant vessels in the Baltic Sea.
Soviet aircraft bombed Finnish vessels and harbours and dropped mines into Finnish seaways. Still, Finnish losses were relatively low, numbering 26 merchant vessels, only four of which were lost inside Finnish territorial waters.
In addition to its navy, Finland had coastal artillery batteries to defend important harbours and naval bases along its coast. Most batteries were left over from the Russian period, with 1521NaN1 guns being the most numerous. However, Finland attempted to modernise its old guns and installed a number of new batteries, the largest of which featured a 3051NaN1 gun battery originally intended to block the Gulf of Finland to Soviet ships with the help of batteries on the Estonian side.
The first naval battle took place on 1 December, near the island of Russarö, 5km south of Hanko. That day, the weather was fair and the visibility excellent. The Finns spotted the Soviet cruiser and two destroyers. After the ships were at a range of 24km, the Finns opened fire with 2341NaN1 coastal guns. After five minutes of firing by four coastal guns, the cruiser had been damaged by near misses and retreated. The destroyers remained undamaged, but Kirov suffered 17 dead and 30 wounded. The Soviets already knew the locations of the Finnish coastal batteries, but were surprised by their firing range.
The coastal artillery had a greater effect upon the land war by helping to reinforce the defence in conjunction with army artillery. Two sets of fortress artillery made significant contributions to the early battles on the Karelian Isthmus and in Ladoga Karelia. These were located at Kaarnajoki on the eastern isthmus and at Mantsi on the northeastern shore of Lake Ladoga. Furthermore, the fortress of Koivisto provided similar support from the southwestern coast of the isthmus. Coastal artilleries had the ability to fire high-explosive shells of 1521NaN1 calibre to a range of 25km.
See main article: Foreign support in the Winter War.
World opinion largely supported the Finnish cause, and the Soviet aggression was generally deemed unjustified. The World War had not yet directly affected France, the UK or the US, the Winter War was the only real fighting in Europe at that time and thus held major world interest. Several foreign organisations sent material aid, and many countries granted credit and military materiel to Finland. Nazi Germany allowed arms to pass through Sweden to Finland, but after a Swedish newspaper made this fact public, Adolf Hitler initiated a policy of silence towards Finland, as part of improved German–Soviet relations following the signing of the Molotov–Ribbentrop Pact.
Volunteers arrived from various countries. By far, the largest foreign contingent came from neighbouring Sweden, which provided nearly 8,760 volunteers during the war. The Swedish Volunteer Corps (Svenska Frivilligkåren), formed from the Swedes, the Norwegians (727 men) and the Danes (1,010 men), fought on the northern front at Salla during the last weeks of the war. A Swedish unit of Gloster Gladiator, named "the Flight Regiment 19" (Lentorykmentti 19, LeR19; 19. flygflottilj, F19). Swedish AA-batteries with Bofors 40mm-guns were responsible for the air defence of northern Finland and the city of Turku. Volunteers arrived from Estonia, Italy and Hungary. Also, 350 American nationals of Finnish background volunteered, and 210 volunteers of other nationalities made it to Finland before the war ended. Max Manus, a Norwegian, fought in the Winter War before returning to Norway and achieving fame as a resistance fighter against the Nazi occupation of Norway. In total, Finland received 12,000 volunteers of whom 50 died during the war.
See main article: Franco-British plans for intervention in the Winter War.
France had been one of the earliest supporters of Finland during the Winter War. The French saw an opportunity to weaken Germany's major ally if the Finns were to attack the Soviet Union. France had other motives as well, because it preferred to have a major war in a remote part of Europe over one on French soil. France planned to re-arm the Polish exile units and transport them to the Finnish Arctic port of Petsamo. Another scheme was to execute a massive air strike with Turkish co-operation against the Caucasus oil fields.
The British, for their part, wanted to block the flow of iron ore from Swedish mines to Germany because the Swedes supplied up to 40% of Germany's need. The matter was raised by the British Admiral Reginald Plunkett on 18 September 1939, and the next day Winston Churchill brought the subject in the Cabinet. On 11 December, Churchill opined that the British should gain a foothold in Scandinavia with the objective of helping the Finns but without a war on the Soviet Union. Because of the heavy German reliance on Swedish iron, Hitler had made it clear to the Swedish government in December that any Allied troops on Swedish soil would immediately provoke a German invasion.
On 19 December, French Prime Minister Édouard Daladier introduced his plan to the General Staff and the British War Cabinet. In his plan, Daladier created linkage between the war in Finland and the iron ore in Sweden. There was a danger of Finland's collapse under Soviet hegemony. In turn, Nazi Germany could occupy both Norway and Sweden. These two dictatorships could divide Scandinavia between them, as they had already done with Poland. The main motivation of France was to export the European battle front to Scandinavia in order to protect French soil, whereas the British were concerned with reducing the German war-making ability.
The Military Coordination Committee met the next day in London, and two days later the French plan was put forward. The Supreme War Council elected to send notes to Norway and Sweden on 27 December in which they urged the Norwegians and Swedes to help Finland and offer the Allies their support. Norway and Sweden rejected the offer on 5 January 1940. The Allies then came up with a new plan, in which they would demand that Norway and Sweden give them right of passage by citing the League of Nations resolution as justification. The expedition troops would disembark at the Norwegian port of Narvik and proceed by rail toward Finland, passing through the Swedish ore fields on the way. This demand was sent to Norway and Sweden on 6 January, but it too was rejected six days later.
Stymied but not yet dissuaded from the possibility of action, the Allies formulated a new plan on 29 January. First, the Finns would make a formal request for assistance. Then the Allies would ask Norway and Sweden for permission to move the "volunteers" across their territory. Finally, in order to protect the supply line from German actions, the Allies would send additional units ashore at Namsos, Bergen, and Trondheim. The operation would require 100,000 British and 35,000 French soldiers with naval and air support. The supply convoys would sail on 12 March and the landings would begin on 20 March.
See main article: Moscow Peace Treaty.
The Moscow Peace Treaty was signed on 12 March 1940 and went into effect the following day. Finland ceded a portion of Karelia – the entire Karelian Isthmus as well as a large swath of land north of Lake Ladoga. The area included Finland's second largest city of Viipuri, much of Finland's industrialised territory, and significant parts still held by Finland's army – all in all, 11% of the territory and 30% of the economic assets of pre-war Finland. Twelve percent of Finland's population, some 422,000 Karelians, were evacuated and lost their homes.
Finland also had to cede a part of the region of Salla, the Kalastajansaarento peninsula in the Barents Sea, and four islands in the Gulf of Finland. The Hanko Peninsula was leased to the Soviet Union as a military base for 30 years. The region of Petsamo, captured by the Red Army during the war, was returned to Finland according to the treaty.
See main article: Aftermath of the Winter War.
The 105-day war had a profound and depressing effect in Finland. Useful international support had been minimal and had arrived late, and the German blockade had prevented most armament shipments. The 15-month period between the Winter War and the Continuation War was later called the Interim Peace.
After the end of the war, the situation of the Finnish army on the Karelian Isthmus had been the subject of debate in Finland. Orders were already issued to prepare a retreat to the next line of defence in the Taipale sector. Estimates of how long the Red Army could have been held in these kinds of retreat-and-stand operations varied from a few days to a few weeks or to a couple of months at most.
During the period between the war and the perestroika in the late 1980s, Soviet historiography leaned solely on Vyacheslav Molotov's speeches on the Winter War. In his radio speech of 29 November 1939, Molotov argued that the Soviet Union had tried to negotiate guarantees of security for Leningrad for two months. However, the Finns had taken a hostile stance to "please foreign imperialists". Finland had undertaken military provocation, and the Soviet Union could no longer hold to non-aggression pacts. According to Molotov, the Soviet Union did not want to occupy or annex Finland; the goal was purely to secure Leningrad.
Another source later used widely in Soviet historiography was Molotov's speech in front of the Supreme Soviet on 29 March 1940, in which he blamed Western countries for starting the war and argued that they had used Finland as a proxy to fight the Soviet Union. The Western Allies had furthermore tried to take neutral Sweden and Norway along with them. Thus, the "masterminds" behind the war were the UK and France, but also Sweden, the U.S., and Italy, who had issued massive amounts of materiel, money, and men to Finland. According to Molotov, the Soviet Union was merciful in peace terms, as the problem of Leningrad security had been solved.
The Supreme Military Soviet met in April 1940, reviewed the lessons of the Finnish campaign, and recommended reforms. The role of frontline political commissars was reduced and old-fashioned ranks and forms of discipline were reintroduced. Clothing, equipment and tactics for winter operations were improved. However, not all of these reforms had been completed when the Germans began Operation Barbarossa 15 months later.
That same year, Finland and Sweden negotiated a military alliance, but the negotiations ended once it became clear that both Germany and the Soviet Union opposed such an alliance.
The Winter War was a political success for the Germans. Both the Red Army and the League of Nations were humiliated, and the Allied Supreme War Council had been revealed to be chaotic and powerless. However, the German policy of neutrality was not popular in the homeland, and relations with Italy had suffered badly. After the Peace of Moscow, Germany did not hesitate to move to improve ties with Finland, and within two weeks Finno-German relations were at the top of the agenda.
During the Interim Peace, Finland established close ties with Germany in hopes of a chance to reclaim areas ceded to the Soviet Union. Three days after the beginning of Operation Barbarossa, the Continuation War began.
The Winter War put in question the organisation and effectiveness of the Red Army as well as the Western Allies. The Supreme War Council was unable to formulate a workable plan, revealing its total unsuitability to make effective war in either Britain or France. This failure led to the collapse of the Daladier government in France.
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