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 ( and ) Five submarines (, , , and ) Four sloops (, , and ) 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 s – used as small torpedo boats, gun boats, sub hunters and in other roles.
Kriegsmarine
Initially, the German Reichsmarine—the Kriegsmarines 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 21 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 , cruisers , , , and , destroyers , , 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.
Soviet Naval Strength in the Baltic June 1941
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.