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The history of the Mannerheim Line

From the early days of independent Finland to the Winter War

Part III


in Part I:

  • The start

  • The "Enckell Line"

  • The fortifying starts again

  • Building the line


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


Part III, includes

The defenses in the "Summankylä"-sector


Note: the map shows the defensive works in the sector, so after a some fighting and artillery bombardment, some of the defensive works (mostly barbed wire) had been destroyed.

The sector of "Summankylä" (translates "the Summa village") was the best fortified defense sector in the whole Karelian Isthmus. The reason was obvious, the main road from Leningrad to Viipuri went right through the small village, and the terrain allowed the mass employment of tanks.


"Talvisodan Historia 2", p.110
"Suomen Linnoittamisen Historia
1918-1944", p.102

The small numbers in the sides of the map represent the height from sea-level.

1 = Field, meadow or otherwise open ground
2 = Forest (both dense and light)
3 = Swamp or marshy ground (including swampy forest)
4 = Concrete fortification (bunker), now showing both mg-bunkers and passive fortifications
5 = Shelter / dugout ( wood & soil)
6 = Entrenched mg-nest
7 = Finnish AT-gun *
8 = Finnish mortar platoon *
9 = Trench for a rifle and lmg-squad
10 = Observation team for mortars
11 = Mined and/or booby trapped area
12 = Barbed-wire obstacle
13 = Tank obstacle (rock rows)
* = The sources didn't specify what difference there was with the AT/mortar -symbol and the encircled AT/mortar-symbol,
so I have to assume it's either an entrenched position or an alternate position (I personally think it's the former).
Note that in these maps, all types woods (tree type and if it's either dense / light) are marked with the same color. And finally, most of these woods had been more or less swept away in the Soviet artillery bombardment, cratering the whole battlefield.

Additional note, there is some contradiction, about the position of certain bunkers (namely Sk.13 and Sk.14, both passive shelters) in different sources, and in case the information differs, the information from the "Suomen Linnoittamisen Historia 1918-1944" has "won" the case.


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The concrete bunkers in Summankylä
(sector abbreviation: "Sk")

Below is a table of the concrete bunkers in Summankylä, divided into two categories depending on the decade when it was built (20s or 30s). The "Frontal-firing bunkers" were, to my best knowledge, all "Enckell" -type bunkers. I've added a link in the bunker #, if I have a model of it in the "Bunker types"-page.

Older fortifications (built before the 1930s)

# old task / type new task / type
1 Frontal-firing  bunker Passive shelter
2 Frontal-firing and accommodation bunker 3 mg flank-firing bunker with accommodation for 26 men
3 Frontal-firing  bunker Flank-firing bunker
4 Frontal-firing  bunker Passive shelter
5 Frontal-firing  bunker Flank-firing bunker
6 Frontal-firing  bunker Flank-firing bunker
7 Frontal-firing  bunker Passive shelter
8 Frontal-firing  bunker Passive shelter
9 Frontal-firing  bunker* (Flank-firing bunker)*
12 Passive shelter Passive shelter
13 Passive shelter Passive shelter
14 Passive shelter Passive shelter
15 Passive shelter Passive shelter

* = the modification work on this "Enckell"-type bunker hadn't started when the war began, so it remained unchanged

Newer fortifications (built in the 1930s)

# Task / type Year of construction
10 3 mg flank-firing bunker*, accommodation for a rifle platoon, mg-chambers had armor plates 1937
11 2 mg flank-firing bunker, accommodation for a rifle platoon 1939
16 Passive shelter for a platoon, Battalion HQ 1939
17 Flank-firing bunker with accommodation for a platoon 1939
18** 2 mg flank-firing bunker (was still under construction when the war started and was not finished)** -
* = had a 4th mg in a special gun mount which could be raised and operated on the bunker roof (a frontal-firing mg)
** = Not visible on the above maps. It was located halfway between Sk 9 and Sk 7

Table source: "Suomen Linnoittamisen historia 1918-1944"


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A panorama from the Summa village
taken from a Soviet 47th Corps artillery observation post.

Picture source: "Talvisodan Historia 2", p.115
Note the Finnish AT-obstacle, the "rock rows" in the middle of the photos


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Two photos taken of bunkers on the eastern side of the Summa village
(January 1940, the right one is with zoom)

Picture source: "Talvisodan Historia 2", p.114


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The fields of fire from the concrete bunkers in the Summa village

The concrete fortifications (also passive shelters in the above map) have been numbered to ease identification. The following table gives more detailed data about them (if you wish to compare the table with the one table in the page "Concrete fortifications in the Karelian Isthmus", the bunkers in this sector had the abbreviation Sk).

Note that in the above maps, the lake on the right is Lake Summa, the same as in the following paragraph, about the "Lähde"-sector. The river is the "Summajoki"-river (or more accurately translated "River Summa").


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The breaking of the line


The Summa village, before and after the fighting

The Summa village before the war, photo taken before the war on 14 November 1939. Note the dwinding River Summanjoki on the left, the shadows of the many barns dotting the fields and the main road running through the village.

A photo taken on 17 February 1940. New roads (dark lines) are clearly visible. The dark sports in the lower middle of the photo are blackened by blown up shelters and bunkers in the Summa village. The red arrows point roughly at the same places.
Source for pictures: "Summa", p.136-137
Note also that the photos are not equal in "zoom", i.e. the photo on the right shows a smaller area


The Soviet 7th Army had concentrated 60 % of it's infantry units and two thirds of it's artillery on a 40 km wide front from Karhula (west of Summa) to lake Muolaanjärvi This gave an average of 2 - 4,5 inf. battalions and 50 -70 artillery pieces per km.

The commander of the Soviet Northwestern front had ordered that the 10 first days of February should be used to conduct small probing attacks and attempts to improve positions for the eventual major attack.
The attacks were conducted by company - battalion strength and were supported by tanks. The Soviet tactics had improved. The tanks didn't make unsupported charges, instead they waited if the infantry didn't follow and they towed them in large armored sledges. The tanks kept distance to the defender's trenches so that the few Finnish AT-guns couldn't fire and the Soviet infantry kept the Finnish infantry AT-teams at bay. The Soviet forces started to systematically destroy the defense works (wire obstacles, AT-obstacles, shelters, bunkers etc.) after they had gained some ground and before the Finnish counterattacks threw them back.

Every day, the Soviet artillery poured shells on the Finnish line, firing in a day more shells than the whole Finnish army had ever had in it's stocks during the war. The Finnish reconnaissance flights revealed scores of "fat targets" in the Soviet rear area, but the Finnish artillery was not allowed to bombard them due to ammo shortage, instead the Finnish artillery had strict orders to open fire only on actual attacks. The Soviet Air Force had every moment dozens of planes in the air increasing the devastation.

The front-line at Lähde sector, where the breakthrough took place. Photographed in 1941.
Picture source: "Summa", p.153
The Soviet artillery fired daily some 300 000 shells in the Summa area alone. In comparison, on Feb. 11th, the day when the Mannerheim Line was breached, the Finnish artillery in the same area fired 5 962 shells.

On Sunday, February 11th, the dawn was hazy but cleared in a few hours. The temperature was -20 ° Celsius, around the same as in the previous days.
At 0840 hrs began a drumfire along the whole sector of the Finnish 3rd Division. Just before noon, the Soviet 100th division started the attack on the Summa-sector, the 138th west of the Summa-sector towards Karhula and the 123rd east of Lake Summa at the Lähde-sector. The attackers were supported by several hundred tanks.


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The "Lähde" sector

Map of the Lähde sector showing the concrete bunkersThe map on the left shows the positions of the concrete fortifications on the "Lähde" -sector, where the Mannerheim Line was breached, and the fields of fire for the machine gun bunkers.

Note that the "Summankylä"-sector, starts just from the western side of Lake Summa.

Table with information of the bunker types and when they were built

# Type Notes
Sj 1 Frontal firing 1 mg bunker built in the 20's
Sj 2 Shelter built during the mobilization
Sj 3 Frontal firing 1 mg bunker built in the 20's
Sj 4 2 mg + shelter for 26 men "Poppius", built in '37, had armor plates *
Sj 5 3 mg + shelter for 40 men "Millions", built in '39
Sj 6 Shelter built in the 20's
Sj 7 "concrete trench" built in the 20's
Sj 8 "concrete trench" built in the 20's
* = had armor plates on the front wall and roof of the machine gun chambers, frontal firing!
Table source: "Suomen Linnoittamisen historia 1918-1944"

The strongpoints in the Lähde sector in December 1939
(as it was manned then by the 1st Bn / JR 13)

Source: "Summa", p.35

The strongpoints at Lähde sector

Strongpoint strength

  1. 2 rifle squads, 2 lmg-squads, 3 mg
  2. 3 rifle squads, 2 lmg-squads, 4 mg, *
  3. 3 rifle squads, 2 lmg-squads, 1 mg
  4. 3 rifle squads, 2 lmg-squads
  5. 4 rifle squads, 3 lmg-squads, 2 mg, **
  6. 2 rifle squads, 3 lmg-squads, 2 mg
  7. 1 rifle squad, 1 lmg-squad, 1 mg
  8. 1 rifle squad, 1 lmg-squad, 2 mg

* = also the command post of a artillery battery commander and an artillery observer
** = also an artillery observer

In addition the battalion had 2 mg in reserve, the mortar platoon had two 81 mm mortars


The deployment of the defending companies on 10 FebruaryThe "Lähde"-sector, east of lake Summa, was defended by the strengthened 2nd battalion of the JR 9 (the 9th Infantry Regiment), a total of some 400 - 500 men on a 4 km wide sector.

The I strongpoint was manned by a infantry platoon, led by 2nd Lt. Leino, from JR 8 and a couple machine guns.

The 4th company, led by Lt. M.G.Ericsson, manned the Finnish right wing, the strongpoints II and III.
Strongpoint II, the notorious "Finger"-strongpoint (situated at the small hill where the Sj 5 bunker "The Million bunker" was located) was particularly subjected to heavy enemy fire and a saying "Life in the Finger is short" was indeed well earned. Unfortunately the eastern mg-casemate of Sj 5 was nearly useless due to the damage sustained during the weeks of bombardment.

The 6th company, led by Lt. Malm, manned the strongpoints IV, V and VI. The bunker "Poppius" (Sj 4) sat right in the middle of the company. But this bunker too was badly mauled and its combat value greatly reduced.

The 5th company, led by Lt. H.V.Hannus, manned the strongpoints VII and VIII. There had been an old (1920s) bunker, Sj 3, near the strongpoint VII, but it had been rendered useless on 15 January after a direct hit by a 6 or 8 inch shell. The VIII strongpoint, also called the Jackboot grove, had lost its shelter in the enemy artillery fire and thus the garrison had to billet in a shelter some 1,5 km in the rear. As the route backwards ran partly through open country, it was both hazardous and straining journey for the men even to get into their positions from their shelter.

The Soviet breach, 11 February 1940By 1130 hrs, all communications were down, and as the Soviet artillery fire shifted from the front-line positions towards the Finnish rear, the enemy infantry attacked. The only working AT-gun in the sector was situated behind the Sj 5. This gun and the few weak Finnish artillery barrages knocked out 6 Soviet tanks, which wasn't nearly enough as dozens of others advanced followed closely by Soviet infantry. As most of the tanks continued their advance into the Finnish rear, 7 tanks began to clear the Finnish positions towards the Sj 5.

The Soviet infantry which had been waiting for the artillery fire to shift not far from the "Finger" (strongpoint II) had managed to capture it quickly but the Finns threw them back around noon. The attack was renewed and again repulsed. Savage fighting raged around the Sj 5 and the "Finger" strongpoint, but the Finns held their positions.

But in the center, the defense wasn't as successful. The Soviet tanks were concentrated near the road and thus the 6th company near Sj 4 (the "Poppius") was fighting a lost battle as they had no AT-guns and the enemy infantry made it impossible to use molotov cocktails or satchel charges. The Poppius was by now out of actions, but the some tanks made things sure and parked themselves in front of the embrasures blocking any possible fire from inside.
Around noon the commander of strongpoint V gave the order to withdraw. The Soviet tanks rolled forward uncontested while some turned east towards the Jackboot grove. To avoid being encircled, the 5th company started to withdraw. By 1300 hrs, the Soviet 123rd division, commanded by Colonel F.F.Aljabushev, had succeeded in capturing one of the Finnish concrete bunkers (the Sj.4 nicknamed "Poppius") and the strongpoints east of it.

A photo taken atop the hill of the "Millions" bunker, facing east towards the "Poppius".
Note the stones of the Finnish antitank obstacle on the right edge of the photo.
From the top of the Millions bunker hill, photo taken in 1943 From the top of the Millions bunker hill, photo taken in 1943 From the top of the Millions bunker hill, photo taken in 1943
From the top of the Millions bunker hill, photo taken in 1943 From the top of the Millions bunker hill, photo taken in 1943 From the top of the Millions bunker hill, photo taken in 1943
From the top of the Millions bunker hill, photo taken in 1943 From the top of the Millions bunker hill, photo taken in 1943 From the top of the Millions bunker hill, photo taken in 1943
Picture source: "Summa", p.152

The defending Finnish battalion, II/JR 9, could offer only scattered resistance, and so by 1900 hrs, the 123rd had advanced to the "back line" of the Finnish positions. The back line was defended by the III/JR 8 and it was strengthened by two engineer companies. The Finnish counterattack by the I/JR 8 was launched at 2000 hrs, and while it started successfully, it ran out of steam by midnight.
The Finnish counterattacks on the next two days were unsuccessful and so the Mannerheim Line was breached. The situation worsened until on February 15th a general order, to abandon the defense positions, was given to the units of the II Corps, now threatened by encirclement.

Some indications of the brutality of the fighting gives the strength of the II/JR 9 on February 13th. The battalion had (a small replacement detachment excluded) only a total of 165 men left in the rifle and mg-companies.



A photo, taken in 1941, of the immediate area around the "Poppius" bunker
Picture source: "Summa", p.152


Go back to Part I

Go back to Part II


See also:

For questions about picture copyrights, see 'Sources' page

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