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The history of the Mannerheim
Line
From the early days of independent Finland
to the Winter War
Part I
(The Finnish Main Defense
Line was baptized "Mannerheim Line" by foreign
journalists during the war. The name was adopted quickly
by the troops and later on officially.)
in Part
II :
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The defensive lines in the Karelian Isthmus
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The mobilization
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The Mannerheim Line ready and powerful?
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The Mannerheim Line in figures
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The concrete bunkers in the Mannerheim Line
- Field fortifications in the Mannerheim Line
in Part
III :
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The defenses in the "Summankylä"-sector
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The concrete bunkers in Summankylä (table)
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A panorama from the Summa village
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Two photos taken of bunkers on the eastern side
of the Summa village
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The fields of fire from the concrete bunkers in the Summa village
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The breaking of the line
The Lähde sector
The strongpoints in the Lähde sector, December
1939
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The start
The history of the Mannerheim Line dates back to the days of the
Finnish civil war (also known as the War of Independence) when the
Finnish Commander In Chief of the White Army, General C.G.Mannerheim,
began to make plans about the defense of the Karelian Isthmus (also
in the text as just "Isthmus") against Russia.
On May 7th 1918, Mannerheim gave an order to investigate and make
preliminary plans for defensive positions. A preliminary plan was
made by two swedes, Lt.Col. A.Rappe and Major K. von Heijne.
It was finished and delivered to Mannerheim's HQ on June 1st 1918.
The plan was eventually ignored, as Mannerheim resigned from the position
of CinC on May 29th, shortly after the plan was ready. An era of German
influence started in the High Command of the Finnish Army.
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| This map shows the Main Defense lines in both Lt.Col.
Rappe's (darker blue near the border) and Col. von Brandenstein's
plans (light blue). Note that both plans incorporated both forward
positions and rear lines, but in order to keep the map more readable
I chose not to include them. |
The next proposal about the position of the soon to be built defense
line was made by a German Colonel, Baron O. Von Brandenstein.
It is interesting that the German plan was a lot more defensive
in nature than the plan made by the Swedes. In fact, the line proposed
was very close to the eventually built Mannerheim Line. This line
was also discarded, but it introduced the idea of using the Vuoksi
- Suvanto lakes as a natural barrier, making also better use of
the many lakes dotting the isthmus (the era of German influence
ended when the German officers left the country at the end of the
year).
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On September 16th 1919, Major General P.O.Enckell became the
Chief of General Staff at the age of 41. He began immediately to study
the different proposals and made his first personal trip to different
sites on his planned defense line in late September.
There was a lot of discussion between high ranking officers of the
Finnish Army about the very idea of making passive fortifications
thereby giving the psychological advantage to the enemy (note that
a very big portion of the Finnish officers were very offensive-minded,
like their German teachers).
But the cruel fact was that Finland was absolutely too poor and lacked
the manpower to defend the Karelian Isthmus without fortifications.
Besides, the use of fortifications decreased the number of men needed
for defense, thereby freeing more men to conduct active operations
against the enemy.
The idea of the "Enckell Line" was to create a chain of
strongpoints that, by the use of carefully placed automatic weapons
(firing from flank fire positions), the enemy was to be stopped by
a relatively small number of men. Their most important objective was
to buy time for the mobilization of the army (at that time the Finnish
"army" could muster 3 ½ divisions without trained
reserves) and to protect the transportation of the army to defend
Viipuri.
There was one person, who contributed much to the overall fortifying
of Finland before the Winter War. This person was Lt.Colonel J.Chr.Fabritius,
who had graduated from the military academy of Hamina and the Military-Engineer
School in St.Petersburg. He had served as a "fortifications officer"
(I am not sure about that translation) in the Russian Army, and was
also a civilian engineer. He made some proposals about the defense
line.
The biggest difference between those two plans was the position of
the frontline in the middle of the Isthmus (the area between Lake
Kuolemanjärvi - Lake Muolaa - Vuoksi). Fabritius put his proposals
to General Theslöf but, according to Lt. General Enckell, they didn not reach the latter before work on the fortifications began.
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The "Enckell Line" is in dark blue,
and the proposal by Fabritius in lighter blue. The major difference
in Fabritius's plan was that a defensive position 8 km deep would
have been created to protect the "Karelian Gateway"(the
shaded area) and that the isthmi positions between Vuoksi and
Lake Muolaa would have provided a good base for active operations
in either the Rautu-direction or towards Kuolemajarvi and Uusikirkko.
Again, the map shows only the main defense lines (but since the
Enckell Line's fortifications near Viipuri were built, I have
included them also).
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In the Fall of 1919 a French military commission arrived to help
in the creation and organization of the Finnish army. The commission
was led by Col. G.Gendre and the fortifications expert was
Major J.J.Gros-Coissy. Gros-Coissy was given the task of making
more detailed plans of the fortifications on the Isthmus, and Fabritius
(who was at the moment an employee of Oy Granit Ab) was asked for
his help by the Minister of War. The co-operation between these
two men began on October 21st 1919.
The first phase was to secure the most threatened spots between
the Gulf of Finland and Vuoksi by machine gun- bunkers (in flank
fire positions and interlocking fields of fire). The cost of one
bunker was estimated to be 100 000 - 110 000 Marks and the number
needed was 80. But right from the start, the Ministry of Defense
could only give 6 000 000 Marks for the first phase (a maximum of
60 bunkers). Gros-Coissy solved the problem by proposing that the
bunkers would be built as front-firing bunkers (with a field of
fire between 90 - 120 degrees). Fabritius strongly protested, but
Enckell favored the Gros-Coissy solution.
Enckell insisted, also, that the bunkers should have overhead protection
from artillery and be able to withstand three direct hits by 6 inch
howitzers. This made the overall height of the bunker's front side
2.50 - 2.60 metres, making it difficult to camouflage them. The
concrete used had an average compression strength of 300 kg/cm²
(in 1939, the required compression strength was 450 kg/cm²).
The walls of the bunkers were mostly made of "spare concrete"
(the concrete had no steel reinforcement, instead rocks were mixed
with concrete).
A total of 164 concrete fortifications (111 machine gun- bunkers
with 1 mg, 3 mg-bunkers with 2 mg, 1 gun & mg-bunker, 6 gun-bunkers,
6 fire control bunkers, 27 passive shelters, 10 "concrete trenches")
were made during 1920 - 1924. While Fabritius can be called the
second "creator" of the Enckell line, he also criticized
it quite a lot. He wanted more depth and he also made remarks about
positioning lone bunkers in the middle of fields with no cover.
He was not alone with his criticism. Also the future General Öhquist
criticized the front-firing bunkers, calling them deathtraps.
On September 18th 1924, General Enckell resigned from his office.
There were many reasons for his resignation, but one of them was
the criticism that the idea of fortifying the Isthmus encountered
(the critics accused the fortifications of "killing" the
active/offensive tactics of the army). The built line of fortifications
was called the "Enckell Line" and after 1924 no new fortifications
were build in the Isthmus for a long time.
Back to Top !
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The fortifying starts again
In the summer of 1927, Captain V.A.M.Karikoski made an inspection
tour to the small isthmi in the area between Vuoksi and Lake Muolaa.
After he left his report, dated August 12th 1927, it was shortly
followed by a report from Major E.Voss on August 30th. Neither
proposals led to any action, but it showed that the General Staff
was interested again.
After many proposals and inspection tours, in late 1931, a decision
to build the Main Defense Line was made. It was decided that it
would follow the plans of the "Enckell Line", with the
exception of using plans by Fabritius in the area between Lake Muolaa
and Vuoksi.
The construction started again, after an 8 year pause, in mid-1932.
The construction was concentrated in the Inkilä (Ink) area,
and was performed by the Engineer Battalion ("Pioneeripataljoona")
as a part of training, in order to save costs.
Fabritius was again involved in his beloved task of building fortifications
in the Isthmus to defend the country. He was appointed as the chief
of the new "fortifications office" (Linnoitustoimisto)
on February 21st 1935. He resigned in late 1938, partly as a protest
against the small annual funds, which slowed the fortifying works,
thus endangering national security.
Only after the political situation worsened in middle Europe, did
the fortifying works get more attention from the Finnish general
staff. The number of hired men working on different sites before
the mobilization (YH in early October) was 600 at most. There were
however several sites where, at it's peak, over 3 000 volunteers
worked between June 4th and October 10th 1939.
During the period between 1936 - 1939, 38 old concrete positions
(bunkers and "concrete trenches") were repaired, 11 old
bunkers were modernized (for example, by converting them to flank-
firing bunkers) and 52 new ones were battle-ready when the war started.
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After the pause, the Inkilä-sector was strengthened and between
1932 - 1934, the engineer battalion built 6 bunkers (the 7th was finished
in 1937). The bunkers were of relatively good quality and the roof
was designed to withstand hits by Soviet 152 mm howitzers. The use
of armor plates was introduced in the 5 newest bunkers (bunkers Ink
3 -7). The plates (12 plates) were left over from the construction
sites of 2 coastal batteries (Mäkiluoto and Kuivasaari) and their
size was little over 2 x 3 metres and thickness either 100mm or 150
mm. The plates enabled the wall, where the firing port was located,
to be relatively thin, making it possible to reduce the size of the
firing port considerably. When armor plates were used also on the
roof, the height of the bunker was reduced by metres making it easier
to blend it into the surrounding landscape.
The problem with armor plates was that they were expensive and had
to be bought abroad. After the global price of steel rose (as an example,
the price of steel plates for three bunkers rose from 3,5 Mio to 5,6
Mio Marks), and the adoption of the "Casemate de Bourge"-type
(shielding the flank-firing machine gun port by a "wing")
bunker building, the use of armor plates was abandoned. Instead, the
compression strength of the concrete, used in bunkers made in 1938
and 1939, was increased steadily (to about 450 kg/cm²) and sometimes
even 600 kg/cm² was achieved. The requirements of a normal bunker
was to withstand several hits by 6 inch bombardment, thereby forcing
the enemy to use super heavy guns to destroy them.
The Artillery Inspector General V.
P. Nenonen, was also involved, from the 1920s onward, in the
Isthmus fortifying. He had on several occasions asked what measures
were taken to prevent the enemy from driving tanks to block the machine
gun-ports (as indeed often happened during the war) making the bunker
harmless. He also pointed out to the designers that the enemy could
bring heavy artillery pieces to the frontline and use them to destroy
bunkers by direct fire. (Again, he predicted what would happen, as
the Soviets, in several places during the war, brought heavy 152 mm
pieces within 500 metres from individual bunkers and silenced them
with accurate shots through the firing port or by slowly wrecking
the bunker walls. These were not designed to take such punishment.
Due to shortage of artillery ammunition, the lone guns were not "fat
enough" targets and therefore not neutralized by Finnish artillery.)
No solutions were brought up to overcome these possible threats, other
than belief in AT-obstacles and infantry AT-teams (funny, since Finland
had virtually no AT-weaponry at that time!) and the Finnish artillery.
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Go to Part
II
Go to Part
III
See also:
Proof-read by: Christopher Kennedy. Melbourne,
Australia.
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