The Soviet submarine Baltic Sea campaign in 1943 was launched by the Soviet Navy to harass the strategic iron ore traffic from neutral Sweden to Nazi Germany on the Eastern Front during the WWII.

[1] Preparations were made in winter 1942 to prevent the intrusion of Soviet submarines in the open Baltic for the following year.

The Finnish minelayers Ruotsinsalmi and Riilahti has been actively engaged in the campaign, sinking one submarine each.

On 23 August 1943, during another anti-submarine patrol, Riilahti was sunk by soviet motor torpedo boat TK-93.

No Soviet attempt to break the Axis blockade achieved success: no ship was sunk by Soviet submarines in the Baltic Sea during 1943, making the outcome of the offensive a decisive Axis success.