The German command dispatched the following units in Kotka from the end of June to operate against the local Soviet shipping in the Gulf: U-481, U-748, U-1193, U-242, U-250, U-348, U-370, U-475, U-479, U-679, U-717, U-745, U-1001.

[1] German operations until Moscow Armistice when Finland joined Side with Allies:[2] On 15 July 1944, U-679 was attacked by small Soviet boats: during a gunnery battle, the motor torpedo boat TK-57 suffered damages and two of her torpedoes barely missed the submarine.

After Finland Joined the Allies, The Germans lost their base at Kotka and the Finnish Navy laid other mine fields under Soviet direction.

[4] On 15 October 1944, U-481 sunk with gunfire the Finnish fishing boats Dan, Endla and Maria.

The ship was carrying military equipment, supplies and guns and was heading to Saarenmaa for the Moonsund Landing Operation.

The Finnish ship had just laid the mine barrage "Vantaa-3" together Ruotsinsalmi and was under escort by two Soviet submarine chasers.

German submarines operated in difficult conditions, with large numbers of naval mines and light antisubmarine boats.