At the start of World War I, "Braunschweig" and "Essen" were reactivated and assigned to IV Battle Squadron under the command of Vice Admiral Ehrhard Schmidt, tasked with coastal defense duties. The squadron conducted several sorties into the Baltic Sea to patrol for Russian warships but it saw no action. The ships were also used to guard the mouth of the Elbe in the North Sea in the first year of the war. "Braunschweig" and "Elsass" participated in the early portion of the Battle of the Gulf of Riga in August 1915, where they kept the Russian pre-dreadnought at bay while a Russian minefield in the Irben Strait was cleared, but the Russian forces put up a strong defense. Schmidt decided to withdraw his forces when it became apparent that the mine-clearing had taken too long, and there was not sufficient daylight left for the minelayer to lay a minefield of its own in Moon Sound to block the northern entrance to the gulf. Following the cancellation of the operation, the squadron saw little activity before being disbanded in December.