In 1938, the Australian Commonwealth Naval Board (ACNB) identified the need for a general purpose 'local defence vessel' capable of both anti-submarine and mine-warfare duties, while easy to construct and operate. The vessel was initially envisaged as having a displacement of approximately 500 tons, a speed of at least , and a range of The opportunity to build a prototype in the place of a cancelled Bar-class boom defence vessel saw the proposed design increased to a 680-ton vessel, with a top speed, and a range of , armed with a 4-inch gun, equipped with asdic, and able to fitted with either depth charges or minesweeping equipment depending on the planned operations: although closer in size to a sloop than a local defence vessel, the resulting increased capabilities were accepted due to advantages over British-designed mine warfare and anti-submarine vessels. Construction of the prototype did not go ahead, but the plans were retained. The need for locally built 'all-rounder' vessels at the start of World War II saw the "Australian Minesweepers" (designated as such to hide their anti-submarine capability, but popularly referred to as "corvettes") approved in September 1939, with 60 constructed during the course of the war: 36 ordered by the RAN, 20 (including "Pirie") ordered by the British Admiralty but manned and commissioned as RAN vessels, and 4 for the Royal Indian Navy.