Skirmishes between the rival destroyer screens in the darkness convinced the German fleet commander, Admiral Friedrich von Ingenohl, that he was faced with the Grand Fleet, now deployed in its battle formation. Under orders from Kaiser Wilhelm II to avoid risking the fleet unnecessarily, von Ingenohl broke off the engagement and turned the battlefleet back toward Germany. In August 1915, a special unit from the German fleet attempted to clear the Russian-held Gulf of Riga in order to assist the German Army, which was planning an assault on Riga. To do so, the German planners intended to drive off or destroy the Russian naval forces in the Gulf, which included the pre-dreadnought battleship and some smaller gunboats and destroyers. The German battle fleet was accompanied by several mine-warfare vessels. These ships were tasked with clearing Russian minefields and laying a series of their own minefields in the northern entrance to the gulf, to prevent Russian naval reinforcements from reaching the area. The assembled German flotilla included "Posen" and her three sister ships, the four s, the battlecruisers , , and , and several pre-dreadnoughts, operating under the command of von Hipper, now a Vice Admiral. The eight battleships were to provide cover for the forces engaging the Russian flotilla. The first attempt on 8 August was unsuccessful, as it had taken too long to clear the Russian minefields to allow the minelayer to lay a minefield of her own. On 16 August, "Posen" and "Nassau" led a second attempt to breach the defenses of the gulf, with "Posen" as Admiral Schmidt's flagship. The two dreadnoughts were accompanied by 4 light cruisers and 31 torpedo boats. On the first day of the assault the Germans broke through the Russian forces, but two German light craft—the minesweeper and the destroyer —were sunk. "Posen" and "Nassau" engaged a pair of Russian gunboats, and . "Sivuch" was sunk that day and "Korietz" was severely damaged; the ship managed to limp away but had to be scuttled the following day. On the 17th, "Posen" and "Nassau" engaged "Slava" at long range; they scored three hits on the Russian ship and forced her to return to port. By 19 August, the Russian minefields had been cleared and the flotilla entered the Gulf.