Mannerheim Line

Mannerheim Line


Location: Karelian Isthmus Map

Constructed: 1918–1924 and 1932–1939


Mannerheim Line

Description of Mannerheim Line

Mannerheim Line is a famous line of military defences that stretched across Karelian isthmus on the border between new Finnish Republic and newly established Soviet Union to the South. It was named after Russian- Finnish General Baron Carl Gustaf Emil Mannerheim of German descent and proved more than formidable during 1939- 1940 Winter War (30 November 1939 – 13 March 1940) when armies of Joseph Stalin almost broke their backs trying to capture this line.
The active part of the construction of Mannerheim Line can be divided in two periods. The first part began right after Russian Revolution of 1917 and subsequent Russian Civil War. The first fortifications were fairly basic. Several lines of trenches were protected by White Russian and White Finnish troops. Their only protection were scarcely scattered mine fields as well as barb wire. Their effectiveness of Mannerheim Line was fairly high due to landscape of the Karelian region. Many swamps and bogs in the area proved to be a formidable challenge that most people never dared to challenged. This left only few corridors for the attack. This significantly increased effectiveness of the small armies since their attackers were simply stuck in the numerous bottle necks across the whole Mannerheim Line.
The second period of Mannerheim Line construction lasted roughly from 1932 to 1939 when the war broke out. These defenses were significantly better. Several large concrete and steel bunkers were constructed at the areas where the attack was most probable. These small citadels were interconnected by numerous trenches, underground tunnels and roads for supply and communication. During the Winter War significantly better equipped and larger Soviet Red Army suffered huge casualties in their attempt to take Mannerheim Line. Eventually the war was won by Joseph Stalin, but not after he lost 127,000 men who were either killed or missing.



Carl Gustaf Emil Mannerheim (1867- 1951)

Baron Carl Gustaf Emil Mannerheim, the mastermind behind the Mannerheim Line, made an important mark in the history of the modern independent Finland. Ironically it was an unwilling contributions due to turmoil of the Russian Revolution in the early 20th century. Mannerheim comes from a German family that moved to Sweden in the 18th century and later emigrated to the Russian Empire. After finishing military academy Carl Gustaf Emil Mannerheim eventually rose to the rank of the lieutenant general in the Russian Imperial Army. During coronation of the last Russian Emperor Nicholas II in 1895 he was one of the guards during the ceremony. On the right picture above he is standing on the right side of the emperor with a white star on his chest. During the Russian Revolution Gustaf Emil Mannerheim remained loyal to the Russian Romanoff family and offered a stiff resistance against the Red Army. He even suggested that Finish White Guard (anti- Bolsheviks) should help fight the Lenin's government. This is one of the reasons why Vladimir Lenin (new leader of the newly established USSR) moved the capital of the new Soviet republic to Moscow. Unfortunately his eagerness to help the cause of the White Army went largely ignored by other Russian generals. The Russian Civil War was lost by the anti- Bolshevik coalition and Carl Gustaf Emil Mannerheim continued his service in Finland.


After Finland's independence, Soviet Russia was perceived in Finland as the only possible military threat and Karelia as the most endangered place of defense. Therefore, the defensive fortification of Karelia was considered urgent. The western part was considered the most important fortification on the Karelian isthmus, because in the eastern part there was a water line formed by Vuoksi, Suvanto and Taipaleenjoki, which supported the defense.

The first plan for the Karelian coast defense lines was presented in the summer of 1918 by two Swedish officers on the order of the Chief of the Defense Forces, Mannerheim. The plan for the main line was close to the border and did not conform to the waterways. The following plan was made by a German colonel. This was very close to the line finally built. When Oscar Enckell became Chief of General Staff in 1919, he focused on researching and planning the fortification of the Karelian Strait. Johan Fabritius, a fortress officer in the army of the former Russian Empire, presented him with his own plans. In the fall of 1919, two French officers arrived to work out the details of the alignment.

The first phase in the 1920s
Construction of the base fortifications began in 1920 according to Enckell's policy. He decided to favor casemates firing from those represented in the wide firing sector as strongholds. Their main advantage was cheapness, but Enckell's plan was opposed because the fortification system of several intersecting side-by-side machine guns would be stronger. Despite its financial solution, Enckell was confronted with the view that defense funding should rather be directed to developing the operational capability of the Finnish Defense Forces. When he resigned in 1924, fortification work ceased. To date, armed fortifications had been built on the Karelian isthmus, with 62 machine-gun and 2 artillery cascades on the western isthmus and 20 machine-gun cascades and 6 artillery stations on the eastern isthmus.

The fortification work began again in 1931 and continued until the Winter War. At that time, the plans of the main defense station were postponed partly southeast on the West Strait. In the 1930s, bunkers larger than casemates were built, two to three of which were completed each year. In the late 1930s, casemates built in the 1920s were also modernized, either by transforming them into side-firing bunkers or by various shelters by casting firing openings. Johan Fabritius served as the head of the Fortress Office from 1935 to 1938. At the start of the war, there were 42 machine-gun bunkers at the start of the war, 25 of which were more modern on the West isthmus and 17 older on the East isthmus. The eastern isthmus also had the old 6 artillery stations. The Mannerheim line used 14,520 cubic meters of concrete, while the shorter VT line used about 400,000 cubic meters.

The second phase in the 1930s
Field equipment work began in the late 1930s. Much of the field equipment was built in the summer of 1939 as volunteer work and during YH. A total of 606 machine gun colonies and ditches were built at the main station (438 for the western isthmus and 168 for the eastern isthmus). 331 km of barbed wire barriers were towed (214 km for the western isthmus and 117 km for the eastern isthmus) and 136 km of boulders used as armored barriers were reduced by 136 kilometers (85 km for the western isthmus and 51 km for the eastern isthmus). As the main station was about 140 kilometers long, it received an average of 4 field-fortified machine gun colonies, 2.5 kilometers of barbed wire barriers, and 1 kilometer of armored barriers per kilometer.

Of the length of the main station, 80 kilometers rested on the water body and the land front was about 60 kilometers. The terrain of the line was relatively shallow throughout. Of the soil in front of the land front, 30 per cent was swamp and 70 per cent hard land. About 75 percent of the hard land was forest land and about 20 percent cultivated. The aim was to place a support line 0.5–1 km behind the main station line.

Only the main station had structural strength. The intermediate station and the rear station were mainly field fortified and partly at the design stage.

Structure by blocks
Blocks of the main station during the Winter War

Blocks from the main station of the Mannerheim line from west to east during the Winter War:

There were two coastal artillery forts on the coast of the Gulf of Finland that supported the main station. Saarenpää Fortress was located at the south-southwestern end of Koivistonsaari. Its main weapons were six 254-millimeter and two 152-millimeter cannons. The coastal fortress of Humaljoki was located on the shores of the Karelian coast next to Koivistonsaari. Its main weapons were six 152-millimeter cannons. The task of the forts was to prevent the Soviet navy from entering the Vyborg Bay.

The Inkilä block was a 9-kilometer long line from Kyrönniemen Bay in the Gulf of Finland to the southern tip of Lake Kuolemanjärvi. The Red Army used three names for the Inkilä block: the Suurpentikkälä node, the Inkilä node and the Muurila node. There were seven bunkers in Inkilä. Inkilä received significant fire support from the coastal cannons of the Gulf of Finland.

The Summankylä block was a 4-kilometer-long line from the northernmost bend of the Summajoki River to Summajärvi. The sum village had four casemates and 13 bunkers.

The Summajärvi block was a 2-kilometer-long line between Summajärvi and Munasuo. The Finns have also called it the Lähte block and the Munasuo block, and the Soviets have called it the Intercontinental Resistance Zone. Summajärvi had three bunkers and six casemates.

The Leipäsuo block was an 800-meter-wide strip between the St. Petersburg and Vyborg line and Tassiolampi. The Red Army called the Leipäsuo block a Railway Node. The bread barn had two bunkers with five casemates behind it.

The Suurniemi block was a line about 2 km long from the southwestern shore of Lake Muolaanjärvi to the southwest of Suurniemi. The Red Army called the block Väisänen's resistance node. The block had five armed bunkers.

The lake stock line was more than 30 kilometers long from Muolaanjärvi to Vuoksi's Pasurinlahti, which ran across Yskjärvi, Kirkkojärvi and Punnusjärvi. The line was only field fortified. For example, there were 167 machine gun ditches.

The northern shores of Vuoksi and Suvanto formed a line of defense. The main crossing points of the lakes had a total of six barracks, consisting of artillery stations and machine gun stations.

The Taipale block was a line from Suvanto to Mustaoja and the bend of the Taipaleenjoki and Kaarnajoki rivers. There were eight machine gun missions in the block.

The coastal artillery of Ladoga consisted of the Järisevä coastal fortress and the Kaarnajoki radiator. Järisevä was located in Järisevänniemi, north of the Taipaleenjoki River. There was one 120-millimeter and two 87-millimeter cannons. The Kaarnajoki radiator was located inland, kilometers from the Kaarnajoki River, northeast of Koveroja. There were four 152-millimeter cannons. The coastal artillery of Ladoga provided significant fire support to the block of Taipale.

The fortified blocks of the intermediate station during the Winter War
At the end of November 1939, the main station was moved further south so that the base fortifications between Muolaanjärvi and Äyräpäänjärvi, which had previously belonged to the main station, were marked as part of the intermediate station and the lake base line was established as part of the main station.

The lane of the Muolaan isthmus was about three kilometers wide between Muolaanjärvi and Äyräpäänjärvi. There were 12 old casemates and 12 bunkers completed by February 1940.

The Salmenkaida lane was about 9 kilometers long on the northern shore of the Salmenkaitajoki between Äyräpäänjärvi and Vuoksi. The Red Army called it the Ritasaari Resistance Node. There were eight old casemates and a bunker completed by February 24, 1940.

The battles of the Winter War
The Karelian army was responsible for the defense of Karelia. The focus was on the Western Strait, which was defended by the Second Army Division with four divisions. The East Strait had the 3rd Army Corps with two divisions. At the beginning of the Winter War, protection forces had been concentrated on the Karelian coast, the task of which was to delay the attacker until the field army could be stationed in the main station. The main station was then tasked with repelling all attacks.

Fighting in the main station
The first offensive of the Red Army
The task of the 7th Soviet Army was to break the positions of the Finns, conquer Vyborg and proceed to the level of Helsinki and Päijänne. According to the Red Army, the best route of attack on the Karelian coast was a narrow lane from Valkeasaari to Vyborg according to the St. Petersburg-Vyborg line.


The Winter War began on November 30, 1939, and the Finnish Defense Forces withdrew to the main station by December 10. On the western isthmus, Soviet 7th Army troops reached a central position south of Lake Muolaanjärvi on December 12 and began their first burglary attempt on December 17. An attempt to cross the Taipaleenjoki River began on the eastern isthmus on 6 December. The Red Army infantry attacked the forts with the support of artillery and the Air Force. The bunkers withstood cannon fire well and the bombings were inaccurate. One radiator fired 1,800 grenades per bunker, only succeeding in removing small pieces from it. The attacker's progress remained modest and the losses large. The 7th Army suspended the offensive on 26 December.

Another offensive of the Red Army
On January 7, 1940, the Red Army formed the Northwestern Front to take on the task of advancing in the direction of Vyborg. The front consisted of the 13th Army, which was tasked with breaking the Mannerheim Line on the East Strait, and the 7th Army, which was now focused only on the West Strait.

On February 1, the Northwest Front launched a major offensive that focused on the Western isthmus in the blocks of Summankylä and Summajärvi. The main station began to break in Summa on February 11, when the Red Army managed to siege and detonate several base fortifications.

The Commander-in-Chief of the Finns gave permission to leave the main station on 15 February. The next night, a retreat was started from the east side of the breakthrough site from the main station between Lake Muolaanjärvi and Vuoksi to the transferred intermediate station at the level of Lake Äyräpäänjärvi. Withdrawal from the Inkilä block began on 16 February without combat contact to avoid blockade. The Humaljoki Fortress was withdrawn on 19 February and the Saarenpää Fortress on 23 February.

On the eastern isthmus, all casemates in the Taipale block were destroyed or lost to the Red Army in January 1940 at the latest. One of Suvanto's fortifications was abandoned shortly before the end of the war. On March 11, the Finns began to detach artillery and crew from the main station to the rear lines of defense. On the eastern isthmus, however, the main station lasted until the end of the war.

Fighting in the midfield
On the western isthmus, the intermediate position proved to be weaker than the main position because its base fortifications were less frequent and outdated, and the terrain was less favorable to the defender. The midfield defense lasted nine days.

The Finns began to withdraw from the intermediate position of the Western Isthmus to the rear position on February 27 at the behest of the Isthmus Army. At that time, most of the base fortifications of the Muolaan isthmus strip and the Salmenkaida strip were Destroyed.

Fighting in the background
When the defenders moved to the rear position on the West Strait, it was poorly equipped and its field fortifications unfinished. In Vyborg Bay, the rear station was concretely unsafe.

In the battle of Vyborg Bay, the Red Army reached the rear position on March 1, when its patrols tried to invade Teikarsaari. The Red Army passed the rear station in the Vyborg Bay on March 3, when the Finns withdrew from Teikarsaari less than a day after the battle. The weak rear position delayed the attacker's progress across the Gulf of Vyborg to the mainland by only a week, when the Finns gave up the rear position in the Vyborg Bay by March 10 at the latest. Inland, the Red Army rose for the first time in Häränpähtiemi on March 2 and received its first permanent bridge headquarters in Vilaniemi on March 5.

In front of Vyborg, the Red Army reached the rear position on March 1. Here, the rear station began to break on March 3, when the defender finally lost the nearby islands that belonged to the rear station and a counterattack on land to recapture the lost stations failed.

On the central isthmus, the front line reached the rear position on March 11th.

Mannerheim line after the Winter War
The Soviet Union destroyed the concrete defense equipment when it took possession of Karelia after the end of the war. In the Continuation War, the line was irrelevant, only the northern parts of the line, which belonged to the VT and VKT lines, were rehabilitated in 1943–1944.

The 79-minute documentary Linija Mannergeima, directed by Vasily Belyaev, was premiered in the Soviet Union on April 10, 1940. The filmmakers received Stalin’s 2nd Class Award.