Mine Warfare

Since the days of Peter the Great the main idea for the defence of St. Petersburg (Leningrad) had been closure of Gulf of Finland. This has been done using forts, naval units and finally with mines. The defence system has always been designed against attack from southwest, i.e. from Sweden or Germany. The purpose of forts is to attack enemy landing forces with artillery fire and also protect own mine barrages. On the Finnish side of the Gulf the forts from Ahvenanmaa to Helsinki were for prevention of landings and protection of own bases. In the outer islands and along the Karelian Isthmus forts were for prevention of bombardment of Leningrad. This idea of protection required bases and forts on both coasts of Gulf of Finland.

The purpose of mine barrages is essentialy the same as that of coastal forts with artillery; to prevent or endanger enemy movements. The Baltic Sea is mostly shallow water without tide and the fragmented coastline of southern Finland is particularly suitable for mine warfare. In Baltic Seas mines were first used during the Crimean war; 1854-55 at Kronstadt and 1855 off Helsinki.

The naval mines designed by Immanuel Nobel (father of Alfred Nobel) were simple devices consisting of submerged wooden casks filled with gun powder. The detonator was a glass ampoule with sulphuric acid in lead vessel filled with muriatic powder (mixture of potassium chlorate and fine sugar). During Crimean War Nobel and another great scientist, Moritz Jacobi (German, the inventor of galvanotechnics), constructed mines with mechanic and electromechanic detonators. Anchored below the surface they effectively deterred the British Royal Navy from moving into firing range of St. Petersburg.

In World War I Russian Navy laid several defensive mine barrages on the mouth of Gulf of Finland and along Baltian coast to protect its main bases. These mines were laid at declaration of war. Further Russian mine barrages were laid at Kökar, Märket, Porkkala-Naissaari line, off Helsinki etc. Germany laid several smaller mine barrages along the Finnish coast. The largest barrages Hanko-Hiidenmaa and Porkkala-Naissaari had about 40 000 mines. The Finnish minelayer M 1 laid first mine barrages of independent Finland. This was done in 1919 in northern end of Koivisto Sound to protect the anchorage of British naval forces under admiral Cowan. Clearing the mines laid by Russia and Germany was the main task of the newborn Finnish Navy after World War I. This was done in cooperation with German units. Every country in the Baltic area was responsible for sweeping own waters, and in Finnish territorial waters about 30-40 vessels operated each summer during the years 1919-1923. The Navy cleared 3 000 km2 and destroyed 1 000 mines. The Navy losses were sweepers T 5 in June 1919 and MP 1 on 5 July 1919. Four men were lost during the mine clearance, two men when MP 1 was lost. Two merchantmen were lost.

During World War II at least 46 different mine types 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 anti-sweeping devices. 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.

Winter War

The actions of Soviet Union in fall 1939 were clearly indicating an attack. Finland began to close some of its sea ways and limited foreign shipping to few harbours. First mines were laid in the last week of October:

When Winter War began one of the first tasks was to close most sea ways with mines. During the nights 30.11 to 3.12. following barrages were laid:

The Parliament approved occupation of Ahvenanmaa 1 December and this was done in the following night. The Märket narrows between Ahvenanmaa and coast of Sweden was closed by mines in the beginning of December. The purpose was to prevent Soviet submarines to enter Gulf of Bothnia.

Soviet Union lost submarine S 2 in mines near Märket 3 January.

Motor torpedo boats Raju and Isku laid 16 M/12 mines off Suursaari harbour 12-13 December. 24.12. Finnish Government decided that Estonia was not following neutrality rules and thus it was legal to mine areas and sea ways to Soviet naval bases and attack Soviet warships in Estonian territorial waters. 27.12.1939 submarine Vesihiisi laid 19 S/30 I mines off Paldiski and 1.1.1940 Vetehinen 20 S/30 I mines off Juminda. These were the only offensive mines in Winter War.

Wooden motor mine sweepers were taken out from operations 25.12, because ice was becoming too strong for their hulls. The boats were docked for the winter in Rauma [SPK 2847].

During Winter War Finland laid 1461 mines in Gulf of Finland and Ahvenanmeri. Minelayer Louhi laid about 500 mines and mining tenders about 350 mines.

264 mines were laid in Laatokka. These barrages were [Wih87]:
Code Place Date Mines Laid by
1 Konevitsa south 30.11.-1.12. 49 S/08, depth 2.4 m Minelayer Yrjö
11 Konevitsa sound 30.11.-1.12. 24 HM/S, depth 1.8 m Minelayer Yrjö
2 Konevitsa northeast 1-2.12. 46 S/08 Minelayer Yrjö
3 Mantsi southeast 1-2.12 30 S/08 Minelayer Kiviniemi
26 Ylläppäänlahti 4-5.12. 6 HM/S Motor boats Km 35, Km 37
27 Puikkeenluoto 4-5.12. 7 HM/S Motor boats Km 36, Km 37
21 Off Pusunsalmi 7.12. 5 S/08 Gunboat Aunus
20 Pusunsalmi west 7.12. 4 S/08 Gunboat Aunus
17 Vuoratsu east 7.12. 9 S/08 Gunboat Aunus
16 Pellotsalo 8.12. 20 HM/S Motor boats Ym 31, Ym 32 Mines laid during several trips
(11) Konevitsa sound 8.12. 14 HM/S Minelayer Yrjö Reinforcement of older barrage.
22 Sikosaari east 9.12. 3 HM/S Motor boats Ym 31, Ym 32
23 Sikosaari west 9.12. 5 HM/S Motor boats Ym 31, Ym 32
24 Sortanlahti mouth 9.12. 7 HM/S Motor boats Km 36, Km 37
18 Lahdenpohja sea lane 14.12. 20 Ma-13 Ground relay mines
19 Sortavala sea lane 18.12. 10 Ma-13 Ground relay mines
25 Sortanlahti harbour 21.12. 5 Ma-13 Ground relay mines

Continuation War

The commander of Finnish Naval Forces sent first orders to conduct mine operations 20.6. The Coastal Fleet in Saaristomeri area was ordered to prepare laying barrages No. 74 and 75 and the Separate Naval Detachment in the Gulf of Finland to lay barrages 11, 12, 20, 34, 35 and 37. These barrages were in Finnish territorial waters. The earliest time for these operations was the night 20/21.6. There was confusion between the Finnish headquarters, which barrages would be laid and when. 21.6. at 15.45 the Separate Naval Detachment got orders to lay barrages No 11, 20, 34 and 35 during the night 21/22.6. At 17.00 Navy HQ got order to lay barrage No 74. At 19.15 Separate Naval Detachment got order to lay barrages 34 and 35 and at 20.00 Navy HQ to lay barrages 78, 81 and 87. At 20.00 Separate Naval Detachment got message from Naval Forces HQ that barrage No 12 is cancelled, others will be laid. [SPK 18708]

The first phase of German mine warfare started few hours before operation "Barbarossa". The German naval forces had planned to prevent movement of Soviet Forces between their main bases, Libau, Hanko, Tallinn and Kronstadt. Large mine barrages were laid in the Baltic sea, "Wartburg I-III" between Memel and Öland and "Apolda" and "Corbetha" across the mouth of Gulf of Finland. Finnish Navy assisted by laying small barrages on the Estonian coast and across the Gulf of Finland. Soviet Union countered these by laying its barrages in the mouth of Gulf of Finland and later in the east part of the Gulf and many small barrages on the Finnish coastal lanes.
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 [Kut02]:
  • "Apolda" with 450 EMC contact mines and 550 Sprengboje D anti-sweeping devices in the mouth of Gulf of Finland between Örö and Tahkuna. Mineship Tannenberg had loaded 300 EMC and Brummer 150 EMC mines and Hansestadt Danzig the Sprengbojen. The minelaying began at 22.38 by laying four lines from 59o40'42''N, 22o20'30''E towards Cap Tahkuna in south till 01.09 to position 59o09'24''N, 22o31'14''E. The group turned west and began laying a sparse barrage with 140 EMC and 150 Spr.D. at 01.25 to 03.09 west from the mine lines.
  • "Corbetha" with 400 EMC contact mines with 30 m antenna down and 700 Sprengboje D anti-sweeping devices in the Porkkala - Naissaari gap. The mineships Cobra and Königin Luise had loaded 200 EMC each and Kaiser the Sprengbojen. The operation was started 30 minutes later as planned due to light night and Soviet forces located northeast from Naissaar. The minelaying began at 23.00 five miles east from Porkkala Kallbåda lighthouse 59o51'48''N, 24o28'30''E. The minelaying operation continues to south to position 59o30'N, 24o08'48''E till 00.40. The "Corbetha" lines had 380 EMC and 680 Spr.D. After laying the mine lines the ships turned west and began to lay a sparse barrage with 20 EMC and 20 Spr.D. while returning to north. The minelaying was finished at 01.57.
At the same time German Schnellboots laid magnetic mines in Soela, Irben and Muhu Sounds on the west coast of Estonia. These barrages were strengthened with 200 mines and 100 anti-sweeping devices, when Brummer laid barrage D2 north from Muhu Sound 25/26.6. and barrage D5 east from "Apolda" 3.7. German S-boots and R-boots laid small barrages with magnetic mines around the Estonian islands [Wih87].
A ship hidden.

On the night 22/23.6. the Soviet minelayers Marti and Ural laid first mines on the Hanko-Osmussaari line. This mine barrage was to include over 3000 anchored mines and about 500 anti-sweeping devices [Wih87]. 3.7. Marti laid 500 mines northwest from Naissaari to protect Tallinn naval base [Ekm81].

The Finnish submarines laid mines in Estonian waters under strong secrecy 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 were laid to disturb Soviet transport between Hanko and Tallinn. 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 last barrage laid by Finnish forces in the first phase of mine warfare. The "Valkjärvi" was to become the nucleus of the massive barrage off Juminda peninsula. The "Juminda barrage" caused heavy losses during the evacuation of Tallinn 28/30.8.1941. Largest mine barrages in 1941.

Within two weeks the Gulf of Finland was practically cut off from the rest of the Baltic Sea. The Finnish forces laid following mine barrages in the Gulf of Finland and Ahvenanmeri area [Wih87]:
Code Place Date Mines Laid by
F2 (11) Suurpisi-Järvensaari 21.6.1941 28 M/12 Mining tender Paukku
F2 (20) North from Luppi 21.6.1941 30 M/12 Mining tender Loimu
F8 (34) Jussarö lane 21-22.6.1941 15 M/10, 6 S/Ma/35 Mining tender Miina
F9 (74) North from Morgonlandet 21-22.6.1941 4 Patrol boat VMV 14 Ready at 02.30 [SPK 18708].
F1 (35) Jussarö-Hästö Busö lane 21-22.6.1941 10 S/40
5 S/40
Patrol boats VMV 5, VMV 6
VMV 12
Lines A and B
Line C
78 Kökar 22.6.1941 40 S/I Gunboat Hämeenmaa Barrage was laid 09.20-09.42 [SPK 18725].
81 Nyhamn 22.6.1941 80 S/38, 20 S/SP Minelayer Louhi Order was given by Navy HQ at 04.20. Louhi departed from Jungfruskär. At 06.05 seven Soviet planes attacked Coastal Fleet ships. Barrage was laid 10.34-12.36. Anchored east from Korsö 13.40 [SPK 18725].
F3 North of Kalkgrund - Vaindlo 22.6.1941 20 S/36 Submarine Vesihiisi
F4 North of Mohni 22.6.1941 20 S/36 Submarine Iku-Turso
F5 Löuna-Uhti - Letipea 22.6.1941 20 S/36 Submarine Vetehinen
82 Kobbaklintarna 23.6.1941 30 S/Ma/36 Minelayer Louhi Order was given by Naval Forces HQ 22.6. at 15.00. Departed on 22.6. at 23.10 from Degerby. Barrage was laid 03.44-04.55. Returned to Degerby 08.15 [SPK 18725].
83 Maarianhamina 23.6.1941 6 S/38 Gunboat Uusimaa Order was given by Naval Forces HQ 22.6. at 15.00.
87 23.6.1941 Minelayer Louhi The barrage was laid too far north and therefore many mines remained on the surface. The new German mines were ordered to be exploded and other surfaced mines to be sweeped.
F7 Northeast from Ruuskeri 24.6.1941 18 S/36 Submarine Vesihiisi
F10 South from Ruuskeri 24.6.1941 20 S/36 Submarine Iku-Turso
87a Märket 26.6.1941 91 S/E ant Minelayer Louhi Departed from Finnbo at 13.45. Barrage was laid 16.30-20.00 without problems [SPK 18725].
Kipinola Southeast from Hanko 26.6.1941 200 S/40 Minelayers Ruotsinsalmi and Riilahti On 25.6. departure from Bågaskär sea lane at 21.58. Machine gunned by two bombers at 00.58. Mine barrage was laid 01.10-01.40. 02.00 machine gunned by two planes. 02.05 a periscope was sighted 150 m to right of the ship, zig-zag course. 02.15 many tens of planes were seen to fly towards the coast and they departed to both east and west. 06.20 tied up alongside barge RWL 65 and started loading 100 S/40 mines in the bay east from Porkkala [SPK 18730].
F11 South from Vaindlo 26.6.1941 18 S/36 Submarine Iku-Turso
F12 Southeast from Pien Tytärsaari 26.6.1941 18 S/30 I Submarine Vesihiisi
Kuolemajärvi Northeast from Osmussaari 27.6.1941 100 S/SP, 100 S/40 Minelayers Ruotsinsalmi and Riilahti Departure from Porkkala Rönnskär at 20.05. Mine barrage was laid in fog 00.10-00.43 without problems. At 01.50 a lone 3-engined plane surprised. Fire was opened and several hits were scored. 02.10 Ruotsinsalmi was straddled by six bombs but no hits. 04.57 anchored west from Barösund pilot station. [SPK 18730]
F6 Suursaari - Pien Tytärsaari 28.6.1941 17 S/30 I Submarine Vetehinen Order was given to Lt.Cmd. Kivikuru verbally 27.6. at 15.50 [SPK 18708].
Valkjärvi North by northeast from Juminda. 29.6.1941 200 S/40 Minelayers Ruotsinsalmi and Riilahti Departure from Santahamina at 21.08. Mine barrage was laid 23.35-00.07 without problems. 03.05 anchored east from Santahamina. Securing forces 6 VMV boats, 4 German and 6 Finnish MTB´s [SPK 18730]
F14 (P1) South from Kalkgrund. 9.7.1941 6 RMA Motor torpedo boats Raju, Vinha and Syöksy
F15 (P2) South from Kalkgrund. 11.7.1941 6 RMA Motor torpedo boats Raju, Vinha and Syöksy
F13 North from Lobineem 11.7.1941 18 S/36 Submarine Iku-Turso
The Finnish Naval Forces got some information about Soviet mine barrages. According to Naval Forces HQ War Diary following information was got [SPK 18708]:
28.6.1941 Naval Forces HQ creed message No. 62 at 13.26: The Russians announce that following area has been mined: 59o31'N, 22o55'E; 59o26'N, 23o12'E; 59o23'N. 23o9,5'E; 59o28'N, 22o53'E.
29.6.1941 Naval Forces HQ creed message No. 80 at 16.05: Russian mine barrages in Ristna - Tahkona area:
59o33,5'N, 22o48'E; 59o23'N,
59o33,5'N, 23o05'E; 59o05'N, 22o00'E
59o27'N, 23o05'E; 59o05'36''N, 22o35'12''E
59o27'N, 22o48'E; 59o13'42''N, 22o?E
59o28'N, 23o20'E; 59o?,
NOTE: In the list above all coordinates had not been found out.
30.6.1941 Naval Forces HQ creed message No. 100 at 22.10: The Russians announce that following area has been mined: 58o05'N, 22o00'E; 59o05'36''N, 22o35'12''E; 59o13'42''N, 22o58'E; 59o30'N, 22o19'48''E; 59o30'N, 22o00'E. The following areas are closed: Muhu Sound, Tallinn harbour and Haralaht.
NOTE: The first latitude should be 59o05'N.
1.7.1941 Naval Forces HQ creed message No. 102 at 11.08: The Russians announce that following areas near the "motti" have been mined: 59o42.5'N, 22o55'E; 59o44'N, 23o16'E; 59o31'N, 23o05'E; 59o27'N, 22o48'E; 59o34'N, 22o48'E; 59o34'N, 23o05'E; 59o27'N, 23o05'E. Also, the following sea lanes: near Fläckgrund, Russarö-Örö 2-3 miles west from Russarö, Lappohja lanes to open sea.
2.7.1941 Naval Forces HQ creed message No. 24 at 20.17: The Russians announce following dangerous: 59o42'36''N, 24o22'24''E; 59o46'N, 24o22'E; 59o47'N. 24o42'12''E; 59o44'36''N, 24o42'30''E.

The mouth of the Gulf of Finland was infested with more than 5200 mines and 2000 anti-sweeping devices. In the west was German "Apolda" barrage and to east from it were Soviet barrages, Finnish "Kipinola" and "Kuolemajärvi" and last German "Corbetha" barrage. The area of Estonian islands were infested with German magnetic mines. These mine barrages were to cause many losses to both sides:
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. Destroyer Gordyi was damaged by a mine that exploded in its paravane [Kut02]. These happened in the western sparse barrage [Pla05].
23.6.1941 Soviet minesweeper T 208 was sunk by German magnetic mine in the mouth of Muhu Sound in "Gotha" barrage [Ekm81].
26/27.6.1941 German Schnellboots S 43 and S 106 were lost in Soviet mines between Hanko and Osmussaari. The boats were in outer screen of minelayer Brummer when it was laying mines south from 59o20'N, 23oE and ran into Soviet barrage south from Russarö during the return voyage [Kut02].
1.7.1941 Soviet submarine M 81 was sunk between Hiiumaa and Vormsi islands (59o08.6'N, 22o58.4'E) by a magnetic mine in the "Gotha" barrage [Mor01].
2.8.1941 Soviet submarine S 11 was lost in Soela Sound between Saaremaa and Hiiumaa islands (58o41.3'N, 22o25.4'E) by a magnetic mine in the "Coburg" barrage. Commander was saved by patrol boats. Six hours after the sinking three sailors managed to escape through stern torpedo tube [Mor01].
24-25.8.1941 Submarine M 103 sailed to operate in Ahvenanmeri 13.8. The boat was ordered back 20.8. but it never appeared to the meeting point with escorts. The wreck was found 1999 in 50 m depth eight miles north from island Vormsi. The boat was possibly lost in barrage D2 laid by German minelayer Brummer [Mor01].
13.9.1941 During operation "Nordwind" the Finnish coast defence ship Ilmarinen was sunk southwest from Utö, probably due to two Soviet mines from barrage 26-A.

The Finnish submarines laid several small barrages off the Estonian coast and between Estonian coast and the outer islands of the Gulf of Finland. These mines caused some losses:
30.6.1941 Submarine chaser MO–143 was lost on emerged mine from barrage F3 laid by Vesihiisi on 22.6.1941.
5.7.1941 Latvi an 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 F4 barrage was laid by Iku-Turso22.6.
7.7.1941 s/s Everolanda (3379 BRT) was badly damaged in barrage F5 laid by Vetehinen on 22.6. The steamer hit a sweeped mine that had not been detected and destroyed by minesweepers. Simultaneously another mine exploded in gear of minesweeper T-202 Buj. Buj received insignificant damages.
7.8.1941 s/s Aksel Karl (3500 BRT) was lost because it 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.
8/1941 Estonian steamer Marija was damaged in the coastal sea way and had to be beached.

The second phase of the mine warfare began in the middle of July when Finnish and German forces began to build up the massive "Juminda" barrage. The purpose of the barrage was to prevent movement between Kronstadt and the major Soviet held areas of Tallinn, Hanko and Estonian Baltic islands. The Finnish "Valkjärvi" barrage had forced the Soviet forces to search free areas more to north. Finnish air reconnaissance had detected Soviet sweeping activity and therefore the "Valkjärvi" was to be expanded. When the German units reached coast in the Juminda - Purekari area 8.8. mine laying began. German minelayers Cobra and Königin Luise dropped first mines 8/9.8 west from "Valkjärvi". Wthin a week 889 mines and 379 anti-sweeping devices had been laid [Wih87]. It was noted that the Baltic Red Fleet is able to sweep through the barrages using sweepers with low draught. Therefore new barrages set to 1.2 m or 1.5 m were laid to west and to east from the first mines. These barrages had 482 mines and 357 anti-sweeping devices [Wih87]. The "Juminda" barrage between Juminda point and Kallbådagrunnd consisted finally of 2000 mines and 770 obstacles. In the "Juminda" barrage the German forces laid barrages D10 to D30. Finnish minelayers laid five large barrages, mining tenders one small and submarines one small:
Code Place Date Mines Laid by
F16 Muolaa Mohni 20.7.1941 50 S/40, 35 S/SP, 15 RE/S. Minelayer Ruotsinsalmi Departure from Melkki at 19.15. Secured by two VMV patrol boats and 2 MTB's. Barrage was laid 23.45-00.10 without problems, except dropping of Sprengboje obstacles is difficult. Continuous artillery fire in Kolgalahti bay. At 01.20 four MTB's approached from ahead, passed and stopped and gave the return signal "l" (Lauri). 03.15 return to Katajanokka. Later it was found out that the boats were enemy boats and that the challenge and return signals were known by enemy [SPK 18730].
F17 East from Osmussaari 2.8.1941 18 S/36. Submarine Vesihiisi
F18 Äyräpää South by southwest from Kallbåda 10.8.1941 65 S/E ant., 16 S/40, 70 M/12, 18 M/10, 9 S/06, 23 S/08. Minelayers Ruotsinsalmi and Riilahti Departure from Kruunuvuorenselkä at 19.36. Secured by 7 German Schnellboot and 4 Räumboot and 2 Finnish MTB's. Barrage was laid 22.13-22.58. The position is 0.5 miles south and 0.4 miles west from the planned position because fo compass deviation with mine load. Anchored 01.28 at Söderskär [SPK 18730].
F19 Vuoksi Southwest from Kallbåda 11.8.1941 35 S/E ant., 34 S/40, 42 S/Ma-35, 30 M/12, 54 S/Ma-35-36. Minelayers Ruotsinsalmi and Riilahti Departure at 20.32 from Melkki. Barrage was laid 23.11-23.32. Back in Melkki at 02.00 [SPK 18730].
F20 Perkjärvi Northwest from Juminda 13.8.1941 200 S/08, S/SP and S/Ma-35-36. Minelayers Ruotsinsalmi and Riilahti Departure from Melkki 12.08. at 20.07. Turned back because of fog and continued at 23.40. Passed Söderskär at 01.30, course south. The securing Schnellboots opened fire at 02.40. At 02.45 the minelayers were orderd to retreat at full speed. They returned to Melkki at 05.45. The ships departed to Söderskär 18.20 and laid mine barrage 22.05-22.35. During the return voyage Ruotsinsalmi had steering gear malfunction and Riilahti had to tow a short time. The ships anchored north from Söderskär at 01.45 and were back in Helsinki 05.30 [SPK 18730].
F21 Perkjärvi 2 North by northeast from Juminda 15.8.1941 100 RE/S. Minelayer Riilahti Departure from Jätkäsaari at 19.30. The obstacles were laid 22.45-23.13. Anchored at Söderskär 00.05 because of darkness. Back in Helsinki 05.30 [SPK 18737].
F22 Helisevä Northeast from Juminda 20.8.1941 100 M/12. Minelayer Riilahti Mines were loaded in Kirkkomaa. The ship departed from Helsinki 19.00. The barrage was laid 21.46-22.07. Back in Helsinki at 00.54 [SPK 18737].
F23 Vuotjärvi South from Kallbåda 28.8.1941 24 M/12. Mining tender Miina

In the second phase mines caused heavy Soviet losses during the evacuations of Tallinn and Hanko and for the submarines that were sent to operate against shipping:
11.8.1941 Mine sweeper T 213 was escorting s/s Vjatsheslav Molotov when it hit a mine and sank off Tallinn [Ekm81].
14.8.1941 Mine sweeper T 202 was escorting m/s Sibir when it detonated two mines and sank in "Juminda" barrage [Ekm81].
24.8.1941 Destroyer Engels, mine sweepers T 209 and T 214 and three steamers sank in "Juminda" barrage [Ekm81].
28.-30.8.1941 During evacuation of Tallinn in "Juminda" barrage:
Destroyers Skoryi, Jakov Sverdlov, Kalinin, Artem, Volodarski
Submarines S 5, Щ 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 in mines
10-11.9.1941 Submarine P 1 sailed 9.9. transporting 19.6 tons supplies to Hanko. The boat disappeared and was possibly lost to mine in "Juminda" or "Corbetha" barrage [Mor01].
9/1941 Submarine Щ 319 had been operating off Libau and started return voyage evening 20.9. The plan was to travel together with Щ 320 to the area of Rödskär lighthouse and continue independently to Kronstadt. The boat did not report passing of 21oE or 24oE meridians. The boat did not answer call 30.9. and was possibly lost in "Juminda" or "Corbetha" barrage [Mor01].
10/1941 Submarine Щ 322 departed evening 10.10. to operate in the mouth of Gulf of Finland. The boat was escorted by sweepers and patrol boats to level of Keri lighthouse. The escorts were released 12.10. at 02.30 and the boat was ordered in the morning of 13.10. to attack enemy shipping off the Hiiumaa coast. The boat did not acknowledge the order, did not report passing of 21oE and never returned. The boat was possibly lost to mine in "Juminda" barrage 12.10. as the escorts heard a strong explosion in the direction of the boat [Mor01].
10/1941 Submarine S 8 departed evening 10.10. to operate southwest Baltic Sea. The boat was escorted by sweepers and patrol boats to level of Keri lighthouse. The escorts were released 12.10. at 02.30 and the boat was ordered in the morning of 13.10. to attack enemy shipping off the Hiiumaa coast. The boat did not acknowledge the order, did not report passing of 21oE or 24oE and never returned. The boat was possibly lost to mine in "Juminda" or "Wartburg" barrage. In July 1999 a S-class submarine wreck was found off Öland (56o10.7'N, 16o39.8'E) and then identified as S 8 but it may also be wreck of S 6 that had sailed 6.8. from Tallinn to operate in Karlskrona - Bornholm area [Mor01].
25.10.1941 Mine sweeper T 203 north from Keri, while enroute to Hanko [Ekm81].
31.10.-11.11.1941 Submarine Kalev (former Estonian) disappeared somewhere west from Suursaari, possibly in "Juminda" or "Corbetha" barrage [Mor01].
11/1941 Submarine Щ 324 sailed 2.11.1941 evening from Kronstadt to Utö area to cover Hanko evacuation (position A). From 10.11. it should operate in Memel-Windau area. On the morning 4.11. the boat sailed with convoy to Hanko. In the night 4/5.11. the commander reported passing 22oE and arrival to operating area. The boat was possibly lost in "Apolda" barrage [Mor01].
4.11.1941 Destroyer Smetlivyi was sunk in the "Corbetha" barrage while evacuating Hanko. 93 men of the crew and 270 infantry men were saved by MO-boats and sweeper T 205 [Ekm81].
11.11.1941 Passenger ship Andrei Zdanov (3 800 tons) sunk while returning from abandoned attempt to evacuate Hanko [Ekm81].
14.11.1941 Minesweeper T 206, destroyers Surovyi and Gordyi and submarine L 2 in "Juminda" barrage [Ekm81]. The L 2 had sailed to lay mines in the Danzig bay. The boat travelled with the third Hanko convoy. After passing Suursaari at 01.07 and 01.10 near Keri two mines exploded in the stern but the boat remained afloat. The boat had run into barrage D46 laid by minelayer Kaiser. The convoy continued sailing and due to negligence of commander of the sweeper БTЩ-217 crew of the sinking boat was not taken off. Third mine exploded at 06.17 and the boat sank in position 59o46'N, 25o10.7'E. 50 men perished [Mor01].
Submarine M 98 was sent to operate against shipping between Helsinki and Tallin. The boat was lost somewhere in the Gulf of Finland. Possible reason is mine in "Juminda" barrage D35 or D46 as two explosion were seen from the convoy at 01.57. [Mor01].
21/22.11.1941 A group of small vessels was sailing from Hanko to Suursaari north from the known mine barrages. Netlayer Azimut and sweeper T 35 were sunk with all hands, probably by drifting mines [Ekm81].
24.11.1941 A group of small vessels was sailing from Hanko to Suursaari and sweeper T 54 was sunk with all hands [Ekm81].
3.12.1941 Passenger ship Josif Stalin (7 645 tons) was hit by at least two mines. More mine hits and/or 12 inch coastal artillery hits are possible. The crippled ship drifted two days before it stranded on Estonian coast.

Mines caused also losses to German and Finnish forces in the Gulf of Finland. Finnish coast defence ship Ilmarinen was lost 13.9. during operation "Nordwind" southwest from Utö, probably due to two Soviet mines from barrage 26-A. Minelayer Königin Luise was returning from mine laying operation 25/26.9. when it hit a mine and sank off Helsinki (60o00'N, 24o59'E). The mines were probably laid by MO patrol boats 13.7.1941 (barrage No. 13). The German tug Föhn was lost 21.11. from a convoy to Tallinn. The Finnish minelayers Ruotsinsalmi and Riilahti and gunboats Uusimaa and Hämeenmaa were escorting s/s Erna and Föhn towing another tug Passat. The minelayers cut loose 11 mines and the convoy had to stop because in the dark these could not be seen. Föhn drifted away from the 120-150 m wide lane and was hit by a mine. Erna and Passat miracuously sailed slowly through the barrage while Finnish vessels were sorting out the situation [SPK 18731].

As the Finnish forces were advancing to east it became necessary to limit movement of Soviet Forces in the Viipurinlahti area. The Finnish forces laid four small barrages F25 to F28 in Tuppura - Pulliniemi area 28-30.8. The VMV patrol laid three small barrages in Hanko sea lanes between 25.8. and 1.9. In the late season the mine warfare units laid still more mines to prevent evacuation of Hanko and to prevent escape of Baltic Red Fleet to Sweden to be interned. After the mine laying operations from 29.8. to 25.9. the forces concentrated on sweeping the lanes between Helsinki and Tallinn and along Finland's south coast. In August and September the German Forces laid barrages D31 to D44 in Juminda - Suursaari - Seiskari area. The last German barrage was D46 laid by Kaiser 3.11. southeast from Harmaja off Helsinki. The Finnish forces laid only two barrages "Yksjärvi" and "Seesjärvi". The barrage F29 "Yksjärvi" was laid 3.9. by minelayer Riilahti northwest from Juminda point. It had 84 M/12, S/08 and S/Ma-35-36 mines. The last barrage F30 "Seesjärvi" was laid 12.11. by minelayers Riilahti and Ruotsinsalmi south from Harmaja. It had 43 EMC with antenna down, 74 S/08 and 21 S/Ma-36 and 2 M/12 mines. [Wih87]

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. Finns 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. Submarine barrages in 1942.

In addition there were following mine barrages:

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. Submarine barrages in 1943.

Baltic Red Fleet sent Щ 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. Submarine barrages in 1944.

"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, 14., 16., 19., 21., 24., and 26 April. Minelayer Roland was lost on the fourth 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, gunboat Hämeenmaa, 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. Mining tenders, June 1944.

The mine barrages in the eastern Gulf of Finland were:


Minelayer Ruotsinsalmi laid 37 S/41 mines, 32 RE/S2 and 30 RE/S anti-sweeping devices in the barrage Pistin 1B between 03.03 and 03.28. The position of the barrage is from 60o17.6', 28o50.2' to 60o16.9', 28o50.8' and to 60o15.7', 28o46.7'. The eastern part has more mines and western part more anti-sweeping devices [SPK 18735].


Minelayer Ruotsinsalmi laid 100 S/43 mines in the barrages Pistin 3 and Pistin 4 between 00.52 and 01.19. The position of the barrage is from 60o19.4', 28o24.5' to 60o18.5', 28o26.5' and to 60o17.9', 28o29.1'. The upper part is Pistin 3 and the lower part Pistin 4 [SPK 18735].


Minelayer Ruotsinsalmi laid 60 S/41 and 40 S/43 mines in the barrage Pistin 5. Gunboat Hämeenmaa laid in the barrage Pistin 5 20 RE/S anti-sweeping devices between 00.10 and 00.42. The position of the barrage is west from Tiurinsaari island, from 60o23'08'', 27o22'30'' to 60o25'24'', 27o17'41''. The depth of S/41 mines was 2 m and they were equipped with antennas. The depth of S/43 mines was 1,5 m without antennas. The anti-sweeping devices were dropped south from the mines [SPK 18735][SPK 24083].


Minelayer Ruotsinsalmi laid the barrage Viipuri A containing 70 S/38 II and 20 M/12 mines between 23.36 and 23.56. The barrage begins 200 meters from Suonionsaari, from 60o37.6', 28o31.2' to 60o35.0', 28o28.8' and to 60o34.35', 28o26.9'. One row of mines, distance 75 m and depth 1,5 m. During the minelaying VMV 5 was close to east from Ruotsinsalmi ready make a smoke screen if the enemy begins to fire from east shore of Viipurinlahti. [SPK 18735].


Minelayer Ruotsinsalmi laid the barrage Viipuri B containing 110 S/43 mines between 00.27 and 00.46. The barrage begins southwest from Tuppura island, from 60o33.6', 28o25.3' to 60o31.9', 28o21.9' and to 60o31.5', 28o18.3'. One row of mines, distance 60 m and depth 1,5 m. The barrage was laid without any securing units as all other vessels were occupied with the evacuation of Koivisto. [SPK 18735].


Minelayer Ruotsinsalmi laid the barrage Viipuri C containing 98 S/43 mines between 23.32 and 23.45. The position of the barrage is 2 miles west from Pulliniemi to direction northeast, from 60o33.1', 28o21.3' to 60o35.9', 28o25.1'. One row of mines, distance 60 m and depth 1,5 m. [SPK 18735].


Gunboats Hämeenmaa and Uusimaa secured German MFP barges 194, 258, 259 and 267 when they laid the barrage Pistin 6 between 23.56 and 00.20. While the barges were dropping mines the gunboats fired at 3 MTB's and one boat was seen to burn and explode at 00.10 [SPK 24083].


Gunboat Hämeenmaa secured German forces laying the mine barrage Pistin 7 [SPK 24083].


Gunboat Hämeenmaa secured German forces laying a mine barrage [SPK 24083].


Gunboat Hämeenmaa secured German forces laying a mine barrage [SPK 24083].

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.

The minelayer Ruotsinsalmi ran aground 19.8. and lost its rudder [SPK 20920].

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

The most active ships were:

minelayer Ruotsinsalmi 3967 mines + 541 obstacles
minelayer Riilahti 1733 mines + 599 obstacles
minelayer Louhi 1275 mines
mining tender Miina 336 mines
mining tender Loimu 61 mines
mining tender Lieska 47 mines
mining tender Paukku 28 mines
mining tender Pommi 16 mines
submarine Vesihiisi 112 mines
submarine Iku-Turso 76 mines
submarine Vetehinen 54 mines
motor torpedo boats 158 mines
VMV patrol boats 152 mines

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:


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.


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.


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.


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. Close cover was given by VMV 2, VMV 5 and VMV 6 and outer screen further in south by Soviet MO-boats. 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 sunk.


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 barrage Vantaa 3 with 160 mines south from Russarö. On the return trip Ruotsinsalmi and Louhi sailed in line with 500 m distance. At 12.50 an explosion happened on the starboard side of Louhi approximately on the level of the aft mast. Louhi sank stern first in two minutes. The ship had been hit by an acoustic torpedo shot by German U 370 in grid square 0253. The explosion has been described smooth indicating a influence triggered weapon and not one that exploded by contact. Previously it has been believed that Louhi hit a mine probably laid by U 481 11 November 1944 [Wih94]. It is also claimed that the Soviet officer in charge ordered Louhi to sail over a known Soviet barrage that was supposed to be so deep that crossing was possible [Lap97]. The escorting two Soviet MO-boats saved most of the crew, but eleven Finnish sailors were lost. 33 Finnish sailors and the Soviet liaison officer were saved. The wreck lays upright at 33 metres depth. The position is given as 59o41'N, 23o07'E, about 7.5 miles in direction 140o from Russarö light. The investigations of the wreck showed that the aft deck is missing, the port side of the aft hull is missing and stern gun and stern wheelhouse have flown away.

A line of tug sweepers.

Mine Clearance 1945--

Gallery showing mine clearance. Mine clearance photo gallery page

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. To increase the sweeping force more "Kuha" class motor mine sweepers were built in Porvoo. The boats Kuha 7 to Kuha 14 were delivered in 1945 and Kuha 15 to Kuha 18 in 1946.

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.

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 35 000 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.

This page is maintained by Jari Aromaa.
Last modified 19.7.2011.