Battle of the Gulf of Riga The Battle of the Gulf of Riga was a World War I naval operation of the German High Seas Fleet against the Russian Baltic Fleet in the Gulf of Riga in the Baltic Sea in August 1915 . The operation ' s objective was to destroy the Russian naval forces in the Gulf and facilitate the fall of Riga to the German army in the later stages of the Central Powers ' offensive on the Eastern Front in 1915 . The German fleet , however , failed to achieve its objective and was forced to return to its bases ; Riga remained in Russian hands until eventually falling to the Germans on 1 September 1917 . Prelude . In early August 1915 , several powerful units of the German High Seas Fleet were transferred to the Baltic to participate in the foray into the Riga Gulf . The intention was to destroy the Russian naval forces in the area , including the pre - dreadnought battleship , and to use the minelayer to block the entrance to the Moon Sound with mine s . The German naval forces , under the command of Vice Admiral Hipper , included the four and four s , the battlecruisers , , and , and a number of smaller craft . Battle . On 8 August , the first attempt to clear the gulf was made ; the old battleships and kept " Slava " at bay while minesweepers cleared a path through the inner belt of mines . During this period , the rest of the German fleet remained in the Baltic and provided protection against other units of the Russian fleet . However , the approach of nightfall meant that " Deutschland " would be unable to mine the entrance to the Suur Strait in time , and so the operation was broken off . In the meantime , the German armored cruiser s and were detached to shell the Russian positions at the Sõrve Peninsula in the Saaremaa island . Several Russian destroyers were anchored at Sõrve , and one was slightly damaged during the bombardment . The battlecruiser " Von der Tann " and the light cruiser were sent to shell the island of Utö . On 16 August , a second attempt was made to enter the gulf . The dreadnoughts and , four light cruisers , and 31 torpedo boats breached the defenses to the gulf . On the first day of the assault , the German minesweeper " T46 " was sunk , as was the destroyer . On 17 August , " Nassau " and " Posen " engaged in an artillery duel with " Slava " , resulting in three hits on the Russian ship that prompted her withdrawal . After three days , the Russian minefields had been cleared , and the flotilla entered the gulf on 19 August , but reports of Allied submarines in the area prompted a German withdrawal from the gulf the following day . Throughout the operation , the German battlecruisers remained in the Baltic and provided cover for the assault into the Gulf of Riga . On the morning of the 19th , " Moltke " was torpedoed by the British E - class submarine ; the torpedo was not spotted until it was approximately away . Without time to manoeuver , the ship was struck in the bow torpedo room . The explosion damaged several torpedoes in the ship , but they did not detonate themselves . Eight men were killed , and of water entered the ship . The ship was repaired at Blohm & Voss in Hamburg , between 23 August and 20 September .