During the successful German attack against Riga in the early part of September, 1917, German submarines appeared in the Gulf of Riga and bombarded the city.
In October it also became known that the German raider Seeadler had run ashore on Lord Howe Island (Society Islands) in the Pacific Ocean, leaving forty-seven prisoners on the island in a state of destitution. The crew of the raider afterward seized a motor sloop and a French schooner on which they carried out some further raids. It was later reported that the motor boat had been captured by an unarmed merchantman in one of the outlying islands of the Fiji group.
The armored British cruiser Drake was torpedoed on the morning of October 2, 1917, off the north coast of Ireland. Though she was able to make harbor, she sank later in shallow water. One officer and eighteen men were killed by the explosion of the torpedo. The Drake was a ship of 14,100 tons with a speed of 24.11 knots and had been launched in 1902. She was a sister ship of the Good Hope sunk off Coronel in November, 1914, during the battle with the German Pacific fleet.
Strong German naval forces participated in the fighting in the Gulf of Riga which took place in the middle of October 1917. They were prominent in enabling German troops to land on Oesel and Dagö Islands and later on Moon Island. It was reported that during an engagement between German and Russian naval forces the Germans lost two destroyers, not, however, before they had sunk a Russian destroyer. A few days later the Russian battleship Slava was also reported as having been sunk, while the balance of the Russian Baltic fleet was trapped in the Gulf of Riga.
Amongst the French losses during September, 1917, was the steamer Media of 4,770 tons, which was torpedoed late that month in the western Mediterranean in spite of the fact that she was being convoyed while in use as a transport. Of her crew of sixty-seven and of 559 soldiers on board 250 were reported missing.
Two fast German cruisers on October 17, 1917, attacked a convoy of merchantmen, escorted by two British destroyers, at a point about midway between the Shetland Islands and Norway. The two destroyers as well as nine of the merchantmen were sunk with a total loss of about 250 lives.
On November 1, 1917, a German warship was reported to have been sunk by a mine off the coast of Sweden. British naval forces, operating in the Cattegat, on November 3, 1917, sank a German auxiliary cruiser and ten German patrol vessels. On November 17, 1917, during an engagement off Helgoland one German light cruiser was sunk and another damaged.
A German submarine, during November, 1917, attacked British naval forces, cooperating with the British expeditionary force in Palestine and sank one destroyer and one monitor.
On November 22, 1917, it was announced that the German Government had included in its "barred zone" waters around the Azores and the channel hitherto left open in the Mediterranean to reach Greece, and had extended the limits of the zone around England.
On November 29, 1917, a German torpedo boat struck a mine off the coast of Belgium and sank, all of her crew with the exception of two being lost.