[2] 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.

[3][4] The vessel was initially envisaged as having a displacement of approximately 500 tons, a speed of at least 10 knots (19 km/h; 12 mph), and a range of 2,000 nautical miles (3,700 km; 2,300 mi).

[7] 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 Maryborough) ordered by the British Admiralty but manned and commissioned as RAN vessels, and 4 for the Royal Indian Navy.

[11][1] After the fall of Singapore Maryborough and the flotilla, now including Toowoomba and Ballarat, were engaged in the defense of the Dutch East Indies, raiding oil refineries in Sumatra to deny them to the Japanese and patrolling the southern area of the Sunda Strait, in particular to prevent Japanese landings in small native craft, until 28 February when Commander Cant took the flotilla to Tjilatjap for replenishment.

[14][15] Maryborough paid off in December 1945, and was sold to the Australian General Trading and Shipping Syndicate on 9 May 1947, who renamed her Isobel Queen.