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Examples of different bunkers

Made by the Finns in the Karelian Isthmus during 1920 - 1939

 

 

 

I have divided the different permanent (concrete)-fortifications in here as follows;

 

 

 

 

"Enckell bunker"

The basic MG (machine gun)-bunker, built in 1920 - 1924, the so called "Enckell-bunker" looked like this. They were originally constructed to withstand three hits by a 150 mm howitzer, which made the front of the bunker 2,50 - 2,60 m high. When the original number of bunkers was reduced, the bunkers were changed from flank-firing to front-firing bunkers. The field of fire was normally 90 to 120 degrees wide.
(The bunker on the right, is facing right)
In 1930's tests were made to old "Enckell-bunkers" and it was noticed that they didn't withstand shelling by modern 150 mm guns, so within the limited budget work began to rebuild or change some of the old bunkers into more modern fortifications.

On the left shows how the old front-firing bunker was changed to a passive 10 man shelter. The gun port was cemented in addition of the frontal wall being covered with earth and a layer of rocks.

(For example; Sk 1 and 4)

In some cases the old bunker was changed into a shelter-section of a newer bunker, that was built next to it. These newer bunkers were usually of the "Casemate de Bourge"-type, where the flank-firing machine gun was shielded from direct firing weapons by a "wing" wall..
(The old bunker in gray, and the newer sections in black).

(for example; Sk 5)

This modification (for example Sk 6) required favorable terrain and a lot of time, because as the old bunker was changed into a flank-firing 2 mg-bunker, a new "normal" looking little hill had to be build to shield the bunker from the enemy.

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Gun bunkers

Along the Vuoksi and Suvanto 8 cannon-bunkers were build between 1922 - 1924, and one in the Jänisjoki-line north of Ladoga. 2 of them were small 1-gun bunkers with a fixed gun, and the rest had from 2 to 4 guns (57 mm Caponier and Nordenfelt naval guns, despite that some of the gun bunkers were originally designed to be armed by wheeled field guns).

From taking these gun bunkers into use (along the Vuoksi-Suvanto), Second Lieutenant E.Repo, from the HQ of III Corps, told the following; "...during the mobilization (YH), the Finnish High Command ignored the gun bunkers and some coastal artillery units "found" these fortifications almost by accident". The doors were locked and the keys in the possession of civilians. The bunkers were unarmed, except the bunker in Kiviniemi (which had 1 gun, see the table below. In early November Lt.Col Rikama, the commander of the Taipale sector, suggested them to be armed with Caponier guns, that the Ladoga Coast Defense had in low value places. The Lake Ladoga Coast Defense denied the guns, so the first attempts to arm the gun bunkers ( forts) were with field artillery pieces. Two types were tested, but neither 76 LK and 87 K/95 guns fitted. So when the war started, the bunkers were still without weapons, but in the first days of the war, Ladoga Coast Defense received an order from General HQ to give 14 Caponier and Nordenfelt guns (both were 57 mm). After long talks, the Navy handed over a few extra guns, so the number of guns at the end of the war was 19.

The bigger gun-bunkers had the guns in adjacent chambers side by side. The designer J.Chr.Fabritius wanted the guns in different bunkers apart from each other, but as usual, as it was cheaper to build one bigger bunker than many smaller ones, the guns were positioned under the same roof.
This is the basic type for the gun-bunkers. (In Kiviniemi (Ki) there was one MG and a gun per side, some had two stories, the crew quarters being under the guns.)
This type of a gun bunker was built in the Muolaa (Mu)-sector in 1922 and later also in Läskelä (north of Ladoga on the Jänisjoki defense line. The gun was a 75 mm "Meller"-naval gun.

 

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Armaments of the gun bunkers, 13 March 1940

Place Sector
Abbreviation
Gun model (57 mm) Total
Caponier Nordenfelt
Oravanniemi La - 3 3
Noisniemi No - 4 4
Kiviniemi Ki 1* - 2
Hoviniemi Sa 2 2 4
Kekinniemi Ke 3 1 4
Patoniemi Tai 3 1 4

Total

8 11 19
* = The Kiviniemi bunker had already one 75 mm Meller gun installed before the war began, and after the war started, the bunker received one Caponier gun.

 

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Gun specifications

  57 / 26 K  (Caponier) 57 / 48 No  (Nordenfelt) 75 / 50 M  (Meller)
Caliber, mm 57 57 75
Barrel length, cal 26.3 47.84 50
Total weight, kg app. 750 1 000 2 880*
Max. range, m 3 000 - 4 000 app. 9 000 12 000
Shell weight, kg app. 2.6 app. 4.9 4.9 - 6.3**
Muzzle velocity, m/s 420 628 - 660* 750 - 806**
Additional info
In Russia, the 57 mm Caponier-gun was taken into service in early 1892. When Finland became an independent country, 17 guns were left behind by the Russian troops.

The gun was a short barreled close defense weapon, without a recoil system. It was widely regarded as an unsatisfactory coast defense gun.

Also known as "6 Pounder QF Nordenfelt Coast Defence Gun" (QF meaning quick-firing, as the gun had a theoretical rate of fire of 20 shots/min)

This gun was also taken into service In Russia, 1892. 40 guns were left behind by the Russian troops when Finland became an independent country, making it one of the most numerous coast defense guns in Finland before the WW2.

* = The muzzle velocity varies, depending on the type of the shell.

Russia bought in 1891, the designs of the French Canet gun system. Only the Russian Navy took into service the 75 mm version as a  naval gun. The gun was produced mainly by Obuhov. Many different versions of this gun (naval, coast defense and AA) were produced with different carriages.

The 75 / 50 M had the gun installed on a carriage designed by Capt. A.P.Meller (later a General).

The gun had a theoretical rate of fire of 12 shots/min, but the practical was 10 shots/min.

* = the weight with the armor plate
** = depending of the shell type

Source: "Itsenäisen Suomen rannikkotykit 1918 - 1998"

 

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Bunker of the late 30's

A few of the bunkers, of the late 30's, had as the MG-compartments wall a 320 mm armor plate,
instead of several feet of concrete. The definite advantage that the armor plate offered, was that the bunker could be made much lower, making the bunker easier to camouflage. Also the firing slit could be considerably smaller (only 7 cm high)and narrower, making it safer to operate under artillery fire.
The problem with armor plates was, that they were hard to manufacture and expensive. So after the "Casemate de Bourge"-type wing was taken into use, no more armor plated bunkers were made.

This was a very typical bunker built in the last two years of peace. This bunker was positioned to fire at the attackers flank, had it's firing port shielded by the "wing", had a searchlight and an armored observation cupola. At least three this type of 1 MG -bunkers (the two smaller ports were for close-defense) were built in the Muolaa (Mu) sector.
(Mu 13, 14 and 20)

 

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Multi mg bunker

In the mid to late 30's, the trend in bunker building was to build 2 to 4 flank-firing bunkers connected via an underground tunnel acting also as a crew compartment. Twelve 2 MG-bunkers (which usually were the size of two 1 mg-bunkers "with their backs together") and six 3 MG- bunkers were constructed in the Mannerheim-line.
But, these big "little fortresses" were very expensive, so they were soon dropped in favor of smaller bunkers. The below "Millions"-bunker is one of the biggest.

This was the "Millions-bunker" in the sector Sj. It was nicknamed after the high cost. It was a 3 MG -bunker (two to the left and one to the right, the small slits near the "wings" were for searchlights), and had three armored observation cupolas. In addition to the crews quarters, the bunker offered shelter for a rifle platoon (some 40 men).

In some sources this bunkers is listed as having 4 mg's. It's a matter of opinion which is closer to the truth, as this bunker had a 4th mg in a special gun mount, that could be raised and operated on the bunker roof (frontal firing mg). But as it couldn't be used from inside the bunker, most tables list this bunker as having 3 mg's.

 

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Passive concrete shelter

In addition of so called "active" defense fortifications, some passive bunkers were built. These were regular shelters for up to a platoon's strength, HQ & shelter-bunkers and small artillery observation-bunkers.
   

Also six short stretches of "concrete trenches" were built from 1922 onwards. They had small
squad-sized "closets" in the front bank of the trench.

This type of concrete shelters were built from 1921 onwards. As they were built some 100 - 150 m from the main defense-line, some kind of depth was achieved. They had firing slits for self-defense only. The example on the left was of the biggest type, offering shelter for a platoon. The passiveness gave the option to sink them deep underground, but the level of groundwater restricted this in many occasions. Passive shelters were usually made to 1 - 3 squads, platoon size shelters were not so common.

(The direction to the front-line is "up")

 

 

 

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