In July 1917 the German commerce raider Wolf laid two minefields in Bass Strait. On 5 July 1917, the British freighter SS Cumberland hit one of these mines near Gabo Island and subsequently sank during salvage operations. Other ship disappearances in the 1920s may have been the result of mines laid by the Wolf. The Wolf revisited the area in her civilian livery as the SS Wachtfels, when she loaded wheat at Geelong in May 1921.
In early October 1940 the German commerce raid Pinguin (Penguin) captured the Norwegian tanker Storstad off the northwest coast of Western Australia. The Germans renamed her the Passat and used her as minelayer in Australian waters. In late October 19-both the Pinguin and the Passat laid mines in Bass Strait, leading to the sinking of two allied merchant ships: the British Cambridge nine kilometres off Wilson’s Promontory on 7 November 1940; and the American City of Rayville about nine kilometres south of Cape Otway on 8 November. A party from the Passat may all have landed at Moonlight Head near Cape Otway as several German articles were found soon afterwards.
Throughout 1942 and 1943 Japanese submarines operated in Bass Strait, and were attacked by the RAAF on several occasions. On 4 June 1942 the SS Barwon was attacked near Gabo Island and the SS Iron Crown was torpedoed and sunk the following day in the same area.
In late 1944 the German submarine U862 operated in the western approaches to Bass Strait.