 The flotilla, which varied in size between two and three boats, was used to support the Royal Australian Navy and Royal New Zealand Navy in anti-submarine warfare training, with the operating cost split between the two nations.In the early 1960s, the British Government advised the Australian Government that reductions in the Royal Navy conventional submarine force meant that the 4th Flotilla was to return to the United Kingdom.The impending withdrawal of the British submarine flotilla sparked the fourth attempt to establish an Australian submarine service.