The German dreadnought Grosser Kurfürst underway for Ösel on October 11, with Zeppelin SL20 above. Grosser Kurfürst would strike a Russian mine the next day, but would still participate in the landings that morning before returning to Wilhelmshaven for repairs.
October 11 1917, Tagga Bay–On October 11, the much-rumored German operation to seize the islands in the Gulf of Riga got underway. Troop transports, accompanied by ten dreadnoughts and various other ships of the High Seas Fleet, sailed from Libau [Liepāja] that morning. They approached Ösel [Saaremaa] Island that night; maneuvering a whole fleet at night was difficult, and there were some delays, but the Russian fleet, preoccupied with its own morale problems, did not find detect them. Despite being preceded by a large number of minesweepers, two of the dreadnoughts (along with one of the transports) struck mines just off the coast. Neither of the dreadnoughts were critically damaged, however, and both were still able to assist the landings and were eventually returned to service.
The landings began at dawn on the 12th. The German dreadnoughts engaged the shore batteries at Tagga Bay, one of the few suitable landing sites on the island, and quickly knocked them out, and the landing German troops secured the beaches quickly. They then quickly moved south from the beaches in two main columns. The first was bound for the Sworbe Peninsula, which dominated the entrance to the Gulf of Riga, and which other German ships were busy bombarding. The other headed towards Arensburg [Kuressaare], the island’s capital.
The Russian commander quickly concluded it would be impossible to hold the bulk of Ösel against the Germans, and, early in the evening of October 12, before leaving the island by boat, ordered all troops not on the Sworbe peninsula to head for the only route off the island, the causeway to Moon [Muhu] Island. However, the Germans had realized the importance of this causeway, and had tasked a brigade of bicycle soldiers to secure it. On October 12, they biked over 30 miles from their landing beach and seized the causeway, and prepared to defend it from the retreating Russians coming their way.