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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
:
-
The defensive lines in the Karelian Isthmus
-
The mobilization
-
The Mannerheim Line ready and powerful?
-
The Mannerheim Line in figures
-
The concrete bunkers in the Mannerheim Line
- Field fortifications in the Mannerheim Line
in
Part
III
:
-
The defenses in the "Summankylä"-sector
-
The concrete bunkers in Summankylä (table)
-
A panorama from the Summa village
-
Two photos taken of bunkers on the eastern side
of the Summa village
-
The fields of fire from the concrete bunkers in the Summa village
-
The breaking of the line
The L?hde sector
The strongpoints in the Lähde sector, December
1939
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The start
The history of the Mannerheim Line date back to the days of the Finnish
civil war (also known as the war of independence) when the Finnish
CinC 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 also forward
positions and rear lines, but in order to keep the map more readable
I chose not to include them.
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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's 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 build 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 in 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 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, and had served as a "fortifications
officer" (I'm 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
Kuolema - lake Muolaa - Vuoksi). But Fabritius told his proposals
to General Theslöf, and according to Lt. General Enckell, the
proposals didn't reach Enckell before the order to start the fortification
works was given.
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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've
been created to protect the "Karelian Gateway"(the shaded
area) and that the isthmi positions between Vuoksi and lake Muolaa
would provide 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 fall 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 to
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 mg-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 needed number was 80 bunkers.
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's
solution.
Enckell insisted also, that the bunkers should have overhead protection
from artillery and that it should 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 used concrete 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 mg-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 as 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 summer 1927,
Captain V.A.M.Karikoski
, made 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. Both
proposals didn't lead to any actions, but it shows that the general
staff was interested again.
After many proposals and inspection tours, in late 1931, the future
Main Defense Line was decided to be built. 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 a 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 at 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
'32 - '34, 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 metres 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 "Casemate de Bourge"-type (shielding
the flank-firing mg port by a "wing") bunker building was
adopted, the use of armor plates was abandoned. Instead, the compression
strength of the concrete, used in bunkers made in '38 and '39, 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 1920's onward, in the Isthmus fortifying. He had on several
occasions asked, what measures were taken to prevent the enemy to
drive tanks to block the mg-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 brought, during the war, in several
places 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 wall, 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:
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