| Conflict: | Soviet submarine Baltic Sea campaign in 1942 |
| Partof: | the Baltic Sea campaign of the Eastern Front of World War II |
| Date: | 1942 |
| Place: | Baltic Sea |
| Result: | Limited Soviet success |
| Combatant1: |  Finland Sweden (neutral) |
| Strength1: | 3 Finnish submarines Anti-submarine forces |
| Strength2: | 30 submarines |
| Casualties1: | 18 merchants sunk 4-6 merchants sunk by mines |
| Casualties2: | 12 submarines sunk 6 submarines damaged |
The Soviet Navy launched the Soviet submarine Baltic Sea campaign in 1942 to harass the strategic iron-ore traffic from neutral Sweden to Nazi Germany during World War II. The Soviet Union and the German Reich fought each other on the Eastern Front (1941-1945) during the war. The Allies also launched other operations - especially involving the Royal Navy - against the traffic.
An important element for the Soviet operation was the small island of Lavansaari, located in the Gulf of Finland and able to accommodate the incoming submarines from Leningrad (under siege) as final step before the attempt to penetrate the Axis minefields. Despite neutrality during the WW2, Sweden agreed to the German request to laying extra fields of mines in Swedish waters.[1] The first Soviet attack group consisted in 10 submarines departing from June 1942.[2]
The second Soviet attack group consisted in other 10 submarines, departing from August 1942.
The successes scored by Soviet submarines during the early stage of the campaign prompted a reaction in terms of deployment by Finland of their own submarines Vesihiisi, Vetehinen and Iku-Turso in anti-sub operations.[4] The Soviet offensive in October involved the larger number of submarines (16) but suffered heavier losses with half of the units lost in action, scoring less success.[2]
The overall number of ships sunk by Soviet submarine during this campaign has been evaluated to 18 ships totaling 37 789 tons, in addition to 10 vessels damaged and 4 vessels sunk by mines laid by submarines (in addition to another possible two sunk in 1943 on mines laid the previous year), while the Soviet forces lost 12 submarines with another 6 being damaged. Despite the heavy losses for few victories scored the Germans perceived the campaign as a threat due to the dwindling number of their transport ships and prepared stronger anti-submarine defenses for 1943. Old Soviet sources overestimated the victories scored to 51 vessels sunk (400.000 tons)[1] All considered, the Soviet campaign was costly and managed to sink only a limited number of vessels but the operation accomplished in creating chaos in the Axis naval supply lines forcing alternate trade routes and investment in escort convoys (previously not assigned) and in greater anti-submarine defenses.[2]
A Soviet repetition of a similar campaign was made for 1943, but Axis forces has been strengthened: the exit from the Gulf of Finland was blocked by anti-submarine nets and Soviet submarines suffered heavy losses without penetrating this blockade.[5]