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.

Naval strength in 1941 consisted of: The Finnish Navy used several other vessels (for example, Coast Guard vessels) during the wars: 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.

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.

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.

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.

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.

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 rapid German advance forced the Soviet Navy to abandon its bases along the Baltic coast and evacuate towards Tallinn and Kronstadt.

[2] 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.

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.

During embarkation the ships were under constant attack by German bombers and artillery, which continued as the armada reached the heavily mined Juminda peninsula.

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.

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.

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.

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.

In November 1942, Finnish motor torpedo boats raided the harbor of Soviet-controlled Lavansaari, sinking the gunboat Krasnoye Znamya in shallow water.

Furthermore, on 2 May 1943, while guarding the mine barriers northeast of Hogland, Finnish gunboat Turunmaa was seriously damaged in a Soviet air raid (The ship was refloated and was fully repaired by 23 October 1943.).

Also, on 16 September, a low-flying Ilyushin Il-4 torpedo plane surprised Finnish escort vessels Uisko and Tursas north of Keri lighthouse.

Resisting at the Estonian border, the Axis maintained a minefield blockade until September, when Finland signed peace with the Soviet Union, and Army Group North retreated from Estonia.

Finnish and German light naval forces made repeated raids into the bay, under constant air, artillery and motor torpedo boat attacks.

The naval forces never reached their target area, but their raids helped the defense of the islands in Viipuri Bay by drawing artillery fire, as well as attacks by Soviet aircraft.

The heavy cruiser Prinz Eugen bombarded Red Army positions near Riga, and several U-boats infiltrated the Gulf of Finland, losing six boats to the Soviets.

[15] Also, German auxiliary cruiser Orion sank close to Swinemunde with heavy loss of life taking 2 bombs dropped by a Soviet aircraft.

As the winter progressed, troop and supply movements across the ice became increasingly important, the Finns having surrounded a large Soviet formation on the northern shore of the lake, near Kitilä, in a motti.

The Soviets' first task was the evacuation of Red Army troops trapped against the northern shore of the lake by advancing Finnish forces.

Their first successful operation took place on the frozen lake in spring of 1942, when a Finnish patrol crossed the ice and set fire to some Soviet barges.

They were transferred away as the lake began to freeze over, and did not return the following year, as the Soviets had managed to open a land route to Leningrad in January 1943.

In 1944, however, the Soviet offensive across the River Svir (aimed at capturing Sortavala at the lake's northern end) included a landing at Tuloksa on the eastern shore.