Erich, here´s to you on that Finnish gulf. I´ll send later the site, as the pictures are missing here.
During World War II at least 46 different types of mines were detected in Gulf of Finland. These had about 10 different systems for triggering, including two magnetic and one acoustic types. The belligerent powers laid about 51 600 mines and 12 700 anti-sweeping devices during the War. Germany laid approximately 28 100 mines and 9 350 obstacles. The rest was half and half by Finland and Soviet Union. In addition, Sweden laid almost 4 500 mines on its own territorial waters. In Gulf of Finland majority of mines in 1941 were laid on the mouth of the Gulf and off Juminda in Estonian waters. Later the mines were laid for anti-submarine purposes east from Suursaari and on the Porkkala-Naissaari line. Some offensive barrages were laid between Kronstadt and Lavansaari 1942-1944 and defensive barrages along coast of Karelian Isthmus, Koivisto islands and Bay of Vyborg in 1944.
During World War II the Gulf of Finland was the most heavily mined area. After the war, by the order of the victors, clearing of the mines was Finlands duty. After the Armistice in 1944 some of the most important sea lanes were sweeped. These were mainly routes that Soviets needed to attack Germany. During a 40 days period over 700 mines, drifting mines and anti-sweeping devices were destroyed. Three vessels were lost. Twelve men were lost and nine wounded. During the main cleaning operation in 1945-1950 over 35 000 km2 was sweeped. 9276 mines or anti-sweeping devices were destroyed, about 10% of these were drifting. 28 men were lost and 37 wounded. This sweeping force was second largest in the world with 2 000 men and 200 vessels. Only Japan had a larger force.
It has been estimated that during World War II Finland had at least 46 different mine types from almost ten countries. Most of these were anchored contact mines, but there were also magnetic and acoustic types. Anchored contact mines had two methods for triggering, electromechanic and mechanic. Horned mines were electromechanic. They were triggered by the so-called Hertz device. When a lead horn was bent, a glass ampoule with acid broke creating a battery and electric current triggered the mine. Some of the electromechanic mines had also mechanical horns that closed the circuit. Mechanical mines were triggered when the mine was moved and a lead pendulum was dislodged. A spring actuated device then triggered the mine.
Horned mines could have surface antennas tied to horns. They were lengths of rope suspended by a float. When a passing ship was fouled in the rope, horn was bent and the mine exploded. For antisubmarine mines there were several types of antennas. Some of them were based on galvanic currents. These antennas were made of copper wire and copper buoys. When a steel structure touched copper antenna, a galvanic cell was formed and resulting current triggered a relay and mine detonated. Copper antennas could extend both up and down. A hose trigger was installed around mooring wire. When submarine or sweeping equipment touched the trigger, it moved upwards, closed an electric circuit and mine exploded. To counter these mines Soviet submarines moved very slowly not to move a hose trigger and they were protected with wooden covers to prevent galvanic contact in copper antennas.
I left the winter war part away here
Continuation War
Six German minelayers had arrived in Finnish waters on 14.6.1941 and were disguised as islands and rocks. Upon the codeword "Dortmund" they would start the first naval operations of Barbarossa on 22.6. at 03.15 hours. The minelayers sailed on the evening of 21.6. and laid two mine barrages:
"Apolda" with 581 contact mines and 673 anti-sweeping devices in the mouth of Gulf of Finland
"Corbetha" with 400 contact mines and 700 anti-sweeping devices in the Porkkala - Naissaari gap.
At the same time German Schnellboots laid magnetic mines in Soela and Muhu Sounds on the west coast of Estonia. Later these barrages were strengthened with 200 mines and 100 anti-sweeping devices.
The Finnish submarines laid under strong secrecy mines in Estonian waters on 22, 24 and 26 July. After the Finnish Government had decided that Finland was at war against Soviet Union on 25 July, the minelaying operations were done more openly. The new minelayers Ruotsinsalmi and Riilahti laid 200 mines southeast from Hanko on 26.6. and 200 mines northeast from Osmussaari on 27.6, the "Kipinola" and "Kuolemajärvi" barrages. On the night of 29/30.6 these minelayers laid 200 mines off Juminda peninsula on the Tallinn-Kronstadt sea way. This "Valkjärvi" barrage was the nucleus of the massive barrage off Juminda peninsula. The "Juminda" barrage with 1700 mines and 700 obstacled caused heavy losses during the evacuation of Tallinn 28/30.8.1941. On the night 22/23.6. the minelayers Marti and Ural laid first mines on the Hanko-Osmussaari line. This mine barrage was to include finally over 3000 mines and almost 500 anti-sweeping devices.
Within two weeks the Gulf of Finland was practically cut off from the rest of the Baltic Sea. The mouth of the gulf was infested with more than 5200 mines and 2000 anti-sweeping devices. These mine barrages were to cause substantial losses:23.6.1941 Soviet cruiser Maksim Gorki and First Destroyer Flotilla sailed into German "Apolda" field. Maksim Gorki lost its bow and had to be towed to Tallinn and on 27.6. to Kronstadt. Destroyer Gnevnyi was sunk.
23.6.1941 Soviet minesweeper T 208 was sunk by German magnetic mine in Muhu Sound.
25.-26.6.1941 German Schnellboots S 43 and S 106 were lost in Soviet mines between Hanko and Osmussaari.
1.7.1941 Soviet submarine M 81 was lost at Lainematala.
6.7.1941 Soviet submarine M 99 was lost at Worms.
2.8.1941 Soviet submarine S 11 was lost in Soela Sound.
13.9.1941 Finnish coast cefence ship Ilmarinen was sunk southwest from Utö, probably due to two Soviet mines.
4.11.1941 Soviet destroyer Smetlivyi was lost in "Corbetha" during evacuation of Hanko.
The Finnish submarines laid several small barrages off the Estonian coast and between Estonian coast and the outer islands. These mines caused some losses:30.6.1941 Submarine chaser MO–143 was lost on emerged mine from barrage laid by Iku-Turso on 22.6.1941.
5.7.1941 Latvian steamer Rasma (3200 tons) was struck by mine at Mohni and had to be beached close to this island. German Schnellboots destroyed the ship later. This barrage was laid by Vesihiisi 22.6.
7.7.1941 s/s Everolanda (3379 BRT) badly damaged on barrage laid by Vetehinen on 22.6. Steamer hit sweeped mine not detected and destroyed by minesweepers. Simultaneously in sweep of minesweeper T-202 Buj another mine blow up. Buj received insignificant damages.
7.8.1941 s/s Aksel Karl (3500 BRT) was lost because left sweeped waterway through barrage laid by Iku-Turso on 22.6.
11.8.1941 Soviet destroyer Steregustshi and passenger ship Vjatsheslav Molotov were damaged at Ruuskeri and towed to Tallinn. Vjatsheslav Molotov was damaged in barrage laid by Vesihiisi on 24.6. Explosion was a result of attempt to clear paravane from sweeped mine.
28.8.1941 Soviet submarine Shtsh 301 was lost at Pien-Tytärsaari.
8/1941 Estonian steamer Marija was damaged in the coastal sea way and had to be beached.
Later in the sailing season 1941 the Soviet navy lost in mines several warships and merchantmen:11.8.1941 Mine sweeper T 213 sunk off Tallinn.
14.8.1941 Mine sweeper T 202 sunk in "Juminda" barrage.
24.8.1941 Destroyer Engels, mine sweepers T 209 and T 214 and three steamers sunk in "Juminda" barrage.
28.-30.8.1941 During evacuation of Tallinn in "Juminda" barrage:
Destroyers Skoryi, Jakov Sverdlov,Kalinin, Artem, Volodarski
Submarines S 5, Shtsh 301
Corvettes Sneg, Tsiklon
Guard ship Saturn, patrol boat MO 202, motor torpedo boat TK 103
25 large and 9 smaller merchantmen, most of them by mines
17.9.1941 Submarine P 1 that was transporting supplies to Hanko.
24.9.1941 Submarine Shtsh 319 somewhere in the Gulf of Finland.
10/1941 Submarine Shtsh 322 somewhere in the Gulf of Finland, probably by mine.
21.10.1941 Submarine S 8 somewhere in the Gulf of Finland.
25.10.1941 Mine sweeper T 203 north from Keri, while enroute to Hanko.
30.10.1941 Submarine Kalev (former Estonian) at Keri lighthouse.
11/1941 Submarine Shtsh 324 near Hanko, probably by mine.
11/1941 Submarine M 103 near Hanko, probably by mine.
4.11.1941 Destroyer Smetlivyi while evacuating Hanko.
11.11.1941 Passenger ship Andrei Zdanov (3 800 tons) sunk while returning from abandoned attempt to evacuate Hanko.
14.11.1941 Minesweeper T 206, destroyer Surovyi and submarine L 2 in "Juminda" barrage.
Submarine M 98 somewhere in the Gulf of Finland.
3.12.1941 Passenger ship Josif Stalin (7 645 tons) was hit by at least two mines. More mine hits and/or 12 inch coast artillery hits are possible. The crippled ship drifted two days before it stranded on Estonian coast.
Continuation War - 1942
To counter the Soviet submarine offensive Finland and Germany had agreed on 12.3.1942 for building of two large mine barrages. These were to be laid north and south from Suursaari and in the Porkkala-Naissaari narrows. Finland had suggested laying a submarine net in the Porkkala-Naissaari line, but suitable nets were not available and German command considered this to be unnecessary. Finnish navy would took hand of the barrage north from Suursaari, while Germans would take care of the rest. The main German mine barrage east from Suursaari was known as "Seeigel" and the second one at Porkkala-Naissaari narrows as "Nashorn". Between these mine barrages light naval forces would hunt down enemy boats. Suursaari and Tytärsaari islands were corner stones of the mine barrages. Monitoring of enemy submarine movements were done in these islands and Someri.
The "Nashorn" barrage was laid 9-10.5. and it contained at first 650 mines but it was later increased to over 1200 mines.
The massive "Seeigel" barrage was laid in five events between 20 and 24 May. This barrage was also increased during the sailing season and hit had finally over 3000 contact mines, 244 bottom mines and 1630 anti-sweeping devices.
The Finnish part of the first defence line, the "Rukajärvi" barrage was laid east from Suursaari-Haapasaari line on 23-27.5. This had 619 mines in four rows at different depths. In June it was strenghtened with 160 mines and 123 anti-sweeping devices and later with 476 antisubmarine mines in seven rows.
In addition there were following mine barrages:
"Seehund" west from Lavansaari, 200 mines and 250 anti-sweeping devices. To prevent Soviets clearing routes through "Seeigel"
"Palkjärvi" at Kalbådagrund had 100 mines. It was assumed that enemy submarines would load batteries at this area.
Smaller offensive barrages, "Sauna", "Peninkulma", "Tiger" and "Brummbär", were laid in sea ways between Kronstadt and Lavansaari.
German air force dropped 200 mines in the Kronstadt area.
The "Seeigel" and "Rukajärvi" barrages were protected from sweeping operations by small naval units. For example the Germans used M-class sweepers, converted trawlers (VP, Vorpostenboote) and auxiliary gunboats (SAT, Schwere Artillerieträger).
Soviet Union lost probably five boats in mines, three boats were damaged.
Continuation War - 1943
The Soviet submarines had broken through the mine barrages in the Gulf of Finland too easily in 1942. To keep Soviet submarine force away from Baltic shipping stronger efforts were planned. The barrages would be larger and in addition a double submarine net would be laid from Porkkala to Naissaari, operation "Walross". Reconstruction of the "Nashorn" mine barrage began on 24.4. and it continued till the end of June. The barrage had more than 8 400 mines of which 838 were bottom mines against submarines. The "Rukajärvi" and "Seeigel" barrages were also improved and they had now more than 10 000 mines.
Baltic Red Fleet sent Shtsh and S-class boats to attack trade in Baltic Sea. Not a single one succeeded. Three boats disappeared and were probably lost by mines. One boat was damaged by mine and had to be scrapped.
New purpose-built minelayer Riilahti was lost 23 August off Tiiskeri. It was surprised while searching enemy submarines, and sunk by motor torpedo boat TK 94. 24 men, including commander, Knight of the Mannerheim Cross Osmo Kivilinna were lost. 10 survivors were picked up by patrol boat VMV 1.
In the end of summer "Hurja" class boats of the second MTB flotilla dropped mines in the areas of Diamant shallows, northeast from Seiskari, northwest and southwest from Lavansaari, the "Salpa" barrages.
Continuation War - 1944
The operational plans of Finnish Navy in 1944 included protection of trade, prevention of landings, defence of outer islands and mine warfare. The repair of "Rukajärvi" and "Seeigel" barrages began in March. In addition Finns laid mines east from Suursaari and new "Siili" field with 131 antenna mines on the east beach of Suursaari. The antisubmarine defences were as large as previous year. The "Seeigel" barrage had again over 10 000 mines and anti-sweeping devices. In May operation "Walross" (the submarine net) was done again and the "Nashorn" barrage was repaired.
"Seeigel" was repaired by German units: minelayers Brummer, Linz and Roland, destroyers Z 28, Z 35 and Z 39, torpedo boat T 30 and few M-boats. The mines were laid in seven occasions in April 14., 16., 19., 21. 24., and 26. Minelayer Roland was lost on the fouth trip in Soviet mines.
All the mines that Finns laid in the eastern part of Gulf of Finland were aimed to prevent massive Soviet landing to the rear of forces on the Karelian Isthmus. After the Soviet attack Finnish MTB's laid three small barrages "Möykky 1-3" on the coast 15-17 June. They used 15 German magnetic TMB bottom mines. Ruotsinsalmi, VMV patrol boats and MTB's laid barrages "Pistin 1-5" to protect Koivisto islands 11-20 June. The central area of Koivisto Sound was not mined as the enemy was already on the east coast. Even the old mining tenders were active.
The German mine transport ship Otter arrived evening 20.6. to Kirkonmaa island off Kotka in full load. Immediately 20 PE-2 bombers attacked the island causing heavy damage: Two mine barges exploded, the mine storage hall vanished, all wooden buildings on the shore caught fire and Otter sank by the pier. All the mines and torpedoes in the hall were lost and this caused much troubles for the planned mine barrages.
In Continuation War Finland laid seven times more mines and anti-sweeping devices than in Winter War:
Year 1941 2478
Year 1942 2933
Year 1943 1047
Year 1944 4923, of which 410 after Armistice 4.9.
Year 1945 240
After the Armistice Finland had to lay some mine barrages on Ahvenanmaa area and off Hanko. These operations were ordered by Russians and they started in October. Eight barrages were laid. These barrages included the following:
16-17.11.44.
Örö fairway 36 mines with depth 3 m. Codename of the barrage was Simo 1. It was laid by minelayer Ruotsinsalmi. The mines had mechanical hose triggers, so they were antisubmarine mines. Örö island had coastal artillery battery and west from it is deep water allowing sailing to inner archipelago.
18.11.44.
Barrage Simo 2 was laid 4-15 cable lenghts SW of Storgadden (75 cable lengths W of Jussarö lighthouse) 60 anti-submarine mines with depth 10 m. It was laid on the fairway to Lappohja anchorage by minelayer Louhi. The arrangement was probably 3 lines with 200 m between. Mine type was S/43, and mine distance was 60 m.
18-19.11.44.
The barrage Simo 3 was laid 2 miles S of Gråharu light (75 cable lenghts NE of Jussarö lighthouse) 80 anti-submarine mines with depth 10 m. It was laid by Ruotsinsalmi.
12.1.45.
South from Hanko peninsula 160 mines in two lines. The codename was Vantaa 1, code Vantaa 3 is also used. This barrage was laid by Ruotsinsalmi and Louhi together. The depth setting was 2.5 m. The eastern line had 100 mines of type S/43, the western had 50 mines type S/38, one type S/38 II and 9 mines of type S/43. Mine distance 70 m,distance between lines 50-250 m. On return trip from this operation minelayer Louhi was mined and sunk.
28.1.45.
Barrage Vantaa 2 (also used codename Vantaa 4) was laid by Ruotsinsalmi. It was located also south from Hanko, closer to coast than Vantaa 1. It had 80 moored mines in one line, depth setting 2.5 m. 60 mines type S/43 and 20 mines type S/41, mine distance 40-60 m.
12 January 1945 minelayers Ruotsinsalmi and Louhi had laid 160 mines south from Russarö. The return trip was done through a known Soviet mine barrage, but the Soviet officer in charge of the operation said that the mines were deep. Louhi hit a mine and sank in two minutes. The escorting Soviet MO-boats saved most of the crew, but ten Finnish sailors were lost.
In the end of Continuation War the Navy had five mine sweeper flotillas. Only one of them was capable to sweep influence mines.
During World War II the Gulf of Finland was probably the most heavily mined area in the world. About 60 000 mines and mine anti-sweeping devices had been laid during 1941-1944. Two thirds were German and a half of the rest were Finnish and a half Soviet. By the order of the victors, cleaning of these fell for Finland. About 200 ships and boats were ordered to work. A major problem was to fill the number of required vessels. Soviet Union had confiscated, for example, many of the larger and more seaworthy tugs as war reparations. Training of personnel was another problem as the mine sweeping force was three times that of the war time Navy. Some of the oldest tugs were totally useless in open sea.
After the Armistice in 1944 some of the most important sea lanes were sweeped. These were mainly routes that Soviets needed to attack Germany. During a 40 days period over 700 mines, drifting mines and anti-sweeping devices were destroyed. Three vessels were lost. Twelve men were lost and nine wounded.
In 1945 the sweeper force consisted of 14 flotillas with 228 vessels and over 2000 men. 3500 mines and obstacles were destroyed. Four vessels and five men were lost. Six men wounded.
In 1946 over 4000 mines and obstacles were destroyed. Three vessels were destroyed and two damaged. Two men were lost and 13 wounded.
In 1947 the most difficult minefields had been sweeped and the main task was to clear sea lanes. The number of destroyed mines was only slightly over 600. Still, three men were lost and one wounded.
In 1948 Soviets were not controlling the sweeping job anymore and so the sweeping force was reduced to 70 vessels. Less than 100 mines were destroyed, and only one sweeper was damaged and two of its men wounded.
Last two years resulted in destroying of 28 drifting mines and 11 deep sea (submarine) mines and anti-sweeping devices.
During the whole operation over 35000 km2 had been sweeped. 9276 mines or anti-sweeping devices had been destroyed, about 10% of these were drifting. 28 men were lost and 37 wounded. 10 boats were destroyed and several damaged. After World War II about 400 mine accidents happened in European waters, but not a single one in waters sweeped by Finnish Navy.
Ok.back to "normal" work. Bye!
