At about 1430hrs the German unit, Gruppe Behncke, renewed its advance. The two half-flotillas of minesweepers led the way, one with broken out sweeper gear, followed König, Kronprinz and Kolberg, then Strassburg, Indianola and the four trawlers of Coastal Protection Half Flotilla East, the latter for use as marker boats for important turning points. The torpedoboats formed an anti-submarine screen. Indianola remained considerably removed from the lead ship of the group because she had to recover the motorboats of her III Mine Sweeper Division.
Meanwhile, Augsburg was detached to Arensburg with the support train, preceded by the IV Minesweeper Division and the 3rd S-Half Flotilla with their minesweeper gear broken out. The minesweeper M77 presented the captured Russian barge to a coastal defence trawler to be conveyed away with the train.
At the beginning of Operation Albion there had been two British submarines stationed in the Riga Gulf, based at Rogekul, C27 (Lieutenant Sealy) and C32 (Lieutenant Satow). When the German undertaking began, Captain Cromie, the chief of the English submarines in the Baltic, immediately dispatched another, C26 (Lieutenant Downie), from Hango to the Moon Sound. The evening of 16 October found Lieutenant Sealy to the southwest of the Moon Sound and it was here that he sighted Gruppe Behncke. Submarine C27 was able to get into an attacking position to port ahead of the German battleships, but, when Lieutenant Sealy raised his periscope to take final aim, he found that he had misjudged the speed of the German unit and that König was less than 300 metres distant. Nevertheless, at 1630hrs, C27 fired two torpedoes but both shots missed and to make matters worse, the submarine broke surface between the two German ships. The German ships did not open fire though, believing that the boat was one of their own. Fregattenkapitän Frank, Commander of Kolberg, which was traveling 500 metres astern of Kronprinz, explained the reason for not opening fire thus: ‘It is one of our own that by chance is surfacing close to our line. Don’t shoot. It has been run over. There indeed is misfortune!’ Likewise, the torpedoboats did not drop any depth charges. However a curt signal from König removed all doubt as to the identity of the attacker: ‘Two missed torpedo shots’. The range had been so low that the battleship’s guns had been unable to depress low enough to take aim on the British submarine. Lieutenant Sealy quickly took his submarine to a safe depth and began reloading his torpedo tubes; he reasoned correctly that more German ships would follow. When he came to periscope depth again he was greeted by the sight of a large steamer and quickly he fired one of his two remaining torpedoes at a range of just over 700 metres. The target was Indianola, which was following the group after recovering two damaged motorboats of her minesweeper division, and at around 1645hrs she was struck amidships, beneath the funnel. The engine room and stokehold filled with water and the ship became unmanoeuvrable. She maintained positive buoyancy, however, and was in no immediate danger of sinking. Four torpedoboats were immediately dispatched to hunt the submarine but none of the depth charges they dropped was able to damage C27. The torpedoed tender was towed in to Arensburg.
Meanwhile, Lieutenant Sealy decided the time was right to quit the Riga Gulf, despite the fact that he had one torpedo remaining. After it became dark C27 surfaced but was immediately forced to dive again by German light forces. After a further unsuccessful depth-charging he was able to exit the Gulf and return to Hango.
The submarine C32 had been stationed 1 nautical mile north of Domesnas and during the same afternoon Lieutenant Satow sighted the German unit to the northwest, at a range of some 5 nautical miles. C32 dived and endeavoured to get into a firing position. However, as the submarine manoeuvred in the clear water she was spotted and bombed by a German seaplane, at which point Lieutenant Satow lost contact with the German unit. He correctly deduced that Gruppe Behncke was headed for the Moon Sound and accordingly steered for the southern exit of the Sound during the night. Luckily for the Germans he did not find them in the dark.
During the afternoon of 16 October, Gruppe Behncke pushed forward to the southern exit of the Moon Sound and at about 2026hrs dropped anchor. The German ships were anchored in one long line with torpedoboats at each end. To provide himself with some security, Vizeadmiral Behncke ordered the torpedoboats to extinguish the lanterns of the mine-free channel marker buoys; he then convened a meeting of the BdAdO and the ship and flotilla commanders onboard his flagship, König. The conference was later related by three of the participants. Kontreadmiral Hopman recalled:
Towards 9pm the unit anchored south of Moon Sound. In an immediately convened meeting Admiral Behncke made known his attack plans. The battleships would break through the blockaded area to the west and they would then defeat the Russian ships lying near Kuiwast and the shore batteries, whilst I with the small cruisers should penetrate the Kleinen Sound. The location of the Russian mine barriers was known to us from the map found on the captured Russian destroyer Grom, which two days before had been taken by our torpedobootes in the Kassar Wiek.
Kapitänleutnant Doflein related the meeting as follows:
In the admiral’s cabin on the flagship all the leaders were gathered in the dim light around the sea chart of Moon Sound. Briefly our leader, Vizeadmiral Behncke, outlined his program: ‘With the day’s dawn I will attack the Russian Fleet and shore batteries in the Moon Sound. I suppose, then, that they will give a hot battle and offer stubborn resistance from behind the mine barriers. Therefore the II Minesweeper Flottille should go forward first to pave a mine-free route to the enemy. If the boats come under fire they should continue the advance, however I will immediately push forward with the ships and attempt to surprise and destroy the enemy.
There was obviously some consternation about the English submarines after the attacks on König and Indianola, as reflected in Fregattenkapitän Frank’s account:
In the evening at about 9pm we all anchored in the middle of the sea, south of Moon Sound on a starless night. If a submarine travelled along the lights of the channel it would find us at their end. We were collected by a torpedoboat and taken to a sitting of admirals, commanders and naval staff officers on König. Despite the moonless night the dark ship’s hull with its black smoke cloud was visible from far off. Admiral Behncke gave us sherry and cigarettes. He imparted our roles for the next day for an attack on the southern exit of Moon Sound. The battleships would push forwards towards Moon Sound and its fortifications, the cruisers against the Kleinen Sound and the battery at Woi. Indeed; and the submarines? ‘I have dispatched torpedoboats to extinguish the buoy lights, gentlemen, but apart from that we must allow them to approach’.