 In early September 1917, following the German conquest of the Russian port of Riga, the German navy decided to eliminate the Russian naval forces that still held the Gulf of Riga.The "Admiralstab" (Navy High Command) planned an operation to seize the Baltic island of Ösel, and specifically the Russian gun batteries on the Sworbe Peninsula.On 18 September, the order was issued for a joint operation with the army to capture Ösel and Moon Islands; the primary naval component was to comprise the flagship, "Moltke", along with III and IV Battle Squadrons of the High Seas Fleet.