In August, I Battle Squadron and three battlecruisers were detached from the fleet to temporarily reinforce the German fleet in the Baltic Sea. The Germans planned to clear the Gulf of Riga to facilitate the capture of the city by the Imperial German Army. The Russian Baltic Fleet had stationed the pre-dreadnought and a number of gunboats and destroyers in the gulf, the entrances to which were protected by a series of minefields. The first attempt during the Battle of the Gulf of Riga to breach the minefields and enter the gulf on 8 August was as it had taken too long to clear the Russian minefields to allow the minelayer to lay a minefield of her own. They made another attempt beginning on 16 August, led by "Nassau" and "Posen", along with four light cruisers and thirty-one torpedo boats.A minesweeper and destroyer were sunk that day, and the next day "Nassau" and "Posen" engaged in an artillery duel with "Slava", forcing her to withdraw after scoring three hits. The remaining minesweepers cleared a path into the gulf, but reports of Allied submarines prompted a German withdrawal. The ships then returned to the High Seas Fleet in the North Sea.