The Baltic Sea campaigns were conducted by Axis and Allied naval forces in the Baltic Sea, the Gulf of Bothnia, the Gulf of Finland and the connected lakes Ladoga and Onega on the Eastern Front of World War II. After early fighting between Polish and German forces, the main combatants were the Kriegsmarine and the Soviet Navy, with Finland supporting the Germans until 1944 and the Soviets thereafter. The Swedish Navy and merchant fleet played important roles, and the British Royal Navy planned Operation Catherine for control of the Baltic Sea and its exit choke point into the North Sea.
While operations included surface and sub-surface combat, aerial combat, amphibious landings, and support of large-scale ground fighting, the most significant feature of Baltic Sea operations was the scale and size of mine warfare, particularly in the Gulf of Finland. The warring parties laid over 60,000 naval mines and anti-sweep obstacles, making the shallow Gulf of Finland some of the most densely-mined waters in the world.
Participants
Finnish Navy
The Finnish Navy was a small professional force. Naval strength in 1941 consisted of:
- Two coastal defence ships (Ilmarinen and Väinämöinen)
- Five submarines (Vesihiisi, Iku-Turso, Vetehinen, Vesikko and Saukko)
- Four sloops (Turunmaa, Karjala, Uusimaa and Hämeenmaa)
- Three minelayers
- 12 minesweepers
- Seven motor torpedo boats
The Finnish Navy used several other vessels (for example, Coast Guard vessels) during the wars:
- Four sloops — used mainly as escorts and minesweepers
- Six cutters — smaller vessels used as escorts and minesweepers
- 17 VMV-class patrol boats – used as small torpedo boats, gun boats, sub hunters and in other roles.
Kriegsmarine
Initially, the German Reichsmarine—the Kriegsmarine's pre-war name—suffered from the limitations imposed by post-World War I treaty obligations; by 1935, however, Germany had signed the Anglo-German Naval Agreement, which allowed it to expand considerably. The name Kriegsmarine was adopted the same year. Though a large, powerful, and professional force, it had to divide its assets between several theaters of war, severely limiting the number and size of the ships it was able to deploy in the Baltic Sea.
At the start of the Operation Barbarossa on 22 June 1941 German naval forces in the Baltic Sea consisted of
- 28 Schnellboote
- 5 submarines
- 10 minelayers (mostly converted passenger liners and ferries)
- 3 squadrons of M-class minesweepers
- 3 squadrons of requisitioned minesweepers (trawlers)
- 2 squadrons of R-boats
- 2 squadrons of patrol boats (trawlers)
- 3 Sperrbrecher
- 2 depot ships for minesweepers
- Various naval tugs, transports and other auxiliaries
In September 1941 Germany formed the provisional Baltenflotte, which consisted of the battleship Tirpitz, cruisers Admiral Scheer, Emden, Köln, Leipzig and Nürnberg, destroyers Z25, Z26, Z27 and the 2nd torpedo boat squadron. It had been tasked with destroying the Soviet Baltic Fleet should it try to escape to neutral Sweden. As this did not happen, and aerial reconnaissance showed severe damage to the remaining ships of the Soviet Baltic Fleet, the Baltenflotte was disbanded before October 1941.
Polish Navy
The relatively small Polish Navy suffered greatly from lack of funds, but still managed to field, at the outbreak of war:
- Four large destroyers
- Five submarines
- One large minelayer
- Various smaller vessels
Soviet Baltic Fleet
The Soviet Baltic Fleet was the largest of the four fleets which made up the Soviet Navy during World War II, and was commanded by Vladimir Tributs throughout the war. Though initially having bases only in the eastern corner of the Gulf of Finland, the Red Banner Baltic Fleet was the largest naval power in the Baltic Sea. As World War II progressed, it was able to make use of naval bases in Estonia, Latvia and Lithuania, first under the terms of agreements forced by the Soviet Union in autumn 1939, then by direct access to the bases following the Soviet occupation of the Baltic states in June 1940.
Gains from the peace treaty after the Winter War further helped the Baltic Fleet, as it acquired a base at Hanko, Finland, as well as the coast of the Karelian Isthmus. Liepāja and Tallinn were the main naval bases of the Baltic Fleet prior to Operation Barbarossa.
Other navies on the Baltic Sea
The Swedish Navy was the third largest in the Baltic Sea. Though Sweden stayed neutral during the war, its naval vessels escorted and protected convoys inside Swedish territorial waters, at times attacking hostile submarines with depth charges.
Estonia, Latvia and Lithuania all had small naval forces before World War II. During the occupation and annexation of the Baltic states by the Soviet Union in 1940 these were attached to the Soviet Baltic Fleet.
Campaigns on the Baltic Sea
Operations before 1941
Invasion of Poland
The Polish Navy participated in the Battle of Gdańsk Bay and Battle of Hel in 1939. A few of its surface ships were evacuated to continue the war from Britain (Operation Peking), but most vessels remained in Poland and were sunk by German forces. Polish submarines operated briefly in the Baltic until either internment in Sweden or escape to Britain (see Orzeł incident) in the autumn of 1939. German naval losses during the invasion amounted to a minesweeper.
Operations in 1941
The Winter War and the occupation of the Baltic states had left the Red Banner Baltic fleet in a strong position. It was the largest navy on the Baltic Sea (two battleships, two heavy cruisers, 19 destroyers, 68 submarines, and a naval air arm comprising 709 aircraft) with bases all along the Baltic coast as well as in Hanko. In particular, the long and vulnerable southern coast of Finland was now exposed to the Soviet navy for its full length.
The Finnish Navy had two branches, the old but well-maintained coastal fortifications built by the Russians before World War I (Peter the Great's Naval Fortress), and the actual navy, consisting of two coastal defence ships, five submarines and a number of smaller craft. The Kriegsmarine could provide only a small part of its naval force, as it was tied up in the battle of the Atlantic. Germany's main concern in the Baltic sea was to protect the routes through the Archipelago Sea which supplied its war industry with vital iron ore imported from Sweden.
The Soviet Navy was taken by surprise by the initial German assault on the USSR on 22 June 1941, and suffered heavy losses during the evacuation from the Baltic States and Finland. The Kriegsmarine had started laying mines several hours before the actual start of the invasion, with immediate effect, the Soviet Baltic Fleet losing a destroyer to mines on the second day of the war. The rapid German advance forced the Soviet Navy to abandon its bases along the Baltic coast and evacuate towards Tallinn and Kronstadt.
To guard against a breakout by the Red Fleet, the Germans deployed a large battlegroup—including the new battleship Tirpitz, cruisers, and destroyers—to the Baltic in August–September 1941, and laid a series of minefields across the Gulf of Finland. As the Soviet fleet made no attempt to flee to the Atlantic or neutral Sweden, Germany eventually withdrew its capital ships. Later, the Finnish coastal defence ship Ilmarinen was sunk by mines during Operation Northwind, a failed feint operation. Finnish submarines and surface forces repeatedly attacked Soviet convoys to and from Hanko but with limited success, due to both strong Soviet resistance and equipment failures. A report from Hanko told of a transport arriving with two unexploded Finnish torpedoes jutting from its hull.
As naval bases at Riga and Liepāja were lost to German advances, the Soviet Navy withdrew to Tallinn, which was surrounded by the end of August, forcing the Soviets to conduct an evacuation by sea. To counter this, the German and Finnish navies dropped 2,400 mines, adding to the 600 already in the sea lanes outside Tallinn. German artillery was set up at Juminda peninsula, Finnish and German torpedo boats were put on alert. The Soviet evacuation consisted of 160 ships, which carried 28,000 people (including the Communist leadership and their families, army and navy personnel, and 10,000 Estonians) and 66,000 short tons (60,000 t) of materiel.
The evacuation began on the night of 27 August, at the same time as the first German troops entered the city. During embarkation the ships were under constant attack by German bombers and artillery, which continued as the armada reached the heavily mined Juminda peninsula. At midnight on 28 August the armada ran into the minefields while being attacked by Finnish and German torpedo boats. Casualties were heavy, with 65 of the 160 ships lost, and several more damaged. Of the 28,000 evacuees, 12,400 perished. With relatively small means, the Kriegsmarine and Finnish Navy had dealt a severe blow to the Red Banner Baltic Fleet, which withdrew to the relative safety of the naval mine barriers and coastal fortifications of Kronstadt.
At the start of the war Finnish ground troops isolated the base at Hanko, with its 30,000-man garrison. The front there remained static, with only small scale naval and amphibious actions in the surrounding archipelago. By the end of the summer the Finnish 17th Division, which had made up the bulk of the besieging force, left Hanko for Eastern Karelia. By December 1941 the base was evacuated, having lost its importance due to both the continuing blockade and the rapid German advance toward Leningrad. The evacuation was performed in several convoys, which managed to transport roughly 23,000 troops to Leningrad. The fleet suffered casualties from Finnish minefields and coastal artillery, losing three destroyers and two large transports (Andrei Zhdanov and Iosif Stalin) as well as several smaller vessels. Finnish troops took the abandoned and heavily mined Hanko after the Soviets had left.
Soviet forces withdrew from Beryozovye Islands too and Finnish forces then moved in and constructed forts in the area. While transporting supplies to these forts, the vessel Porkkala ran into a mine on 28 November 1941 and sank. She was later repaired and refitted and recommissioned.
Though naval mines, aerial supremacy, and the rapid German advance on land had largely neutralized its heavy elements, the Soviet Baltic Fleet in the immediate vicinity of Leningrad had not been destroyed. Shore bombardment by the fleet was important in saving Leningrad from the Initial German assault in September. The battleship Marat was sunk by German Junkers Ju 87 Stuka dive bombers in Kronstadt on 23 September, but was partially salvaged for use as a static battery. Many Baltic Fleet sailors fought on land during the Siege of Leningrad. Also, though some of the islands in the bay of Finland had been lost during 1941, the islands of Seiskari and Lavansaari were held, which would prove to be important bases as the war progressed.
Operations in 1942
In 1942, the Baltic Fleet was confined to the innermost part of the Gulf of Finland by German minefields. The Soviets maintained the Oranienbaum Bridgehead and sent several submarines into the open Baltic via Lavansaari island, which now proved an invaluable base for both submarines and light surface forces. Submarines attacked German-Finnish as well as neutral shipping with limited success, sinking 18 ships but losing 12 submarines.
Although the losses inflicted by the Soviet submarines were fairly light, their presence in the Baltic Sea disrupted transportation and forced vessels to use safer coastal waterways instead of faster open sea routes. Continued Soviet submarine operations forced the Germans and Finns to step up their anti-submarine efforts in the Gulf of Finland, and largely due to these efforts, Soviet submariners met increasing hardships and losses, while seeing ever-fewer victories against Axis shipping.
The Soviets had evacuated most of the islands in the Gulf of Finland in late 1941. They recaptured the Suursaari from a small Finnish detachment in January 1942; two months later, a larger Finnish force with strong air cover marched over the ice and drove off the Soviet garrison. Soviet attempts to regain the island resulted in battles which continued over the ice until April 1942. Finnish and German forces also captured lightly defended Tytärsaari. In July 1942, the Soviets attempted to wrest the small island of Someri from the Finnish. In spite of initial success, the Soviet landing force was crushed, and the supporting naval units were repulsed in what proved to be one of the largest surface actions seen on the Baltic Sea during World War II. During this battle, Finnish gunboats Turunmaa and Hämeenmaa were both damaged by Soviet aircraft.
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