In accordance with the Anglo-Japanese Alliance, the fleet helped defend Australia and New Zealand as well as Allied shipping in the Pacific and Indian oceans during World War I.

At the outbreak of war, the Royal Australian Navy (RAN) stood at 3,800 personnel and consisted of sixteen ships, including the Indefatigable-class battlecruiser Australia, the light cruisers Sydney and Melbourne, the destroyers Parramatta, Yarra and Warrego, and the submarines AE1 and AE2.

[2] The Australian government requested help from the British Admiralty, as the remaining warships could not effectively protect the region.

[3] In January 1917, Japan created the 1st Special Squadron, made up of several cruisers supported by the 2nd Destroyer Division.

To provide more coverage, the Japanese Navy formed the 3rd Special Squadron on March 26, 1917, to defend the eastern coast of Australia and New Zealand.