This was a German naval operation in support of Finnish naval activity, using the torpedo boats T 30 and T 31 as well as the smaller craft of Korvettenkapitän Dr Emil Kieffer’s 3rd Minensuch-Flottille, Kapitänleutnant Walter Erich Schneider’s 1st Raumboots-Flottille and Fregattenkapitän Erich Brauneis’s 24th Landungs-Flottille to attack the Soviet maritime delivery of supplies and troop reinforcements for the offensive against Viipuri (Vyborg) on the coast of the Gulf of Finland (15/21 June 1944).
This took place in the course of the part of the Soviet 'Vyborg Offensive Operation' to take the offshore islands of the Karelian isthmus. On 15 June the Finnish IV Corps was compelled to withdraw under fire from the Soviet 59th Army and 21st Army from the 'VT-linja' to Vyborg. The Soviet ground forces received heavy naval fire support from the battleship Oktyabrskaya Revolutsiya, and in an effort to cover their seaward flank, the Finns used their own light naval forces and two submarines, but also called for German support, which was provided by the vessels above in Vyborg Bay and Koivisto Sound. In an attack by Soviet motor torpedo boats T 31 was lost, and in air attacks on 20/21 June one artillery ferry and the mine transport Otter are sunk and M 29, R 119, R 120 and the motor minesweeper tender Nettelbeck were damaged.
The Soviet landings on Koivisto were delayed but not prevented, and by 23 June the islands had been evacuated and occupied by the Soviets, who are supported by a number of warships including the gunboats Volga, Zeya, Kama and Oka.