In 1937, three ships were ordered by the RAN for use as Boom Defense Vessels. The plan was altered in early 1938 to require only two ships; the third, HMAS Kangaroo was earmarked to be constructed as a prototype local defense vessel. The RAN's Director of Engineering was instructed to prepare plans for the ship in July 1938, which were completed six months later. The ship was to weigh 680 tons, with a speed of 15.5 knots, and a range of 2,850 miles. Kangaroo would have been armed with two 4-inch guns and depth charges, and equipped with asdic. The design was based loosely on the United Kingdom's Bangor class minesweepers and Flower class corvettes, but the Australian-designed vessel was larger and better suited for Australian conditions. Before construction could begin, the number of boom vessels was increased back to three, and Kangaroo was laid down to that design.
Although the Kangaroo prototype was never built, the design was retained, and in September 1939 the Australian Commonwealth Naval Board approved the construction of seven ships corresponding to the design. Additional orders were quickly placed by the RAN, the British Admiralty and the Royal Indian Navy, with 60 ships constructed over the course of World War II; 36 were commissioned into the RAN, 20 were manned by RAN personnel but were paid for by the Admiralty, and 4 were built for the Royal Indian Navy. The ships were officially designated "Australian Minesweepers" (AMS) to hide their intended anti-submarine role, although the Bathursts were popularly referred to as corvettes. Although the design was not perfectly suited for any specific role, the all-round general capability for minesweeping, patrol, and escort duties was seen as a good short term solution until better vessels could be requesitioned or constructed.
Construction of the ships required a significant expansion of the Australian shipbuilding industry. This was achieved by bringing disused dockyards back into production and establishing new facilities. The lead shipyard was Cockatoo Island Dockyard in Sydney, which laid down the first ship in February 1940, and produced a further seven vessels. The other seven shipyards involved were Walkers Limited in Maryborough, Queensland (7 ships), Evans Deakin & Co in Brisbane (11 ships), Morts Dock & Engineering Co in Sydney (14 ships), Poole & Steele Limited in Sydney (7 ships), NSW State Dockyard at Newcastle, New South Wales (1 ship), HMA Naval Dockyard at Williamstown, Victoria (8 ships), and Broken Hill Pty Co Ltd at Whyalla, South Australia (4 ships). The initial rate of construction was slow, due to a variety of factors: industrial problems, restrictive work practices, and a lack of qualified labour primary among them. Despite initial predictions that two vessels per month would enter service through 1941, the RAN was advised at the end of 1940 that only seven would be completed by the end of the next year. Rate of construction increased by late 1941, although the increasing need of shipbuilding resources for repairs as the war progressed slowed the rate of construction back down.
The most common armament for Bathurst class corvettes was 1 x 12-pounder gun, 3 x Oerlikon 20 mm cannons, 2 x Lewis .303 machine guns, and 2 x .303 Vickers machine guns. The corvettes carried up to 40 depth charges, which were deployed by 4 throwers and 2 chutes. Some of the corvettes were armed with a 4-inch Mk XIX HA gun instead of the 12-pounder gun, and at a point during the war many of the 12-pounder carrying corvettes were refitted with the 4-inch. Also, on many vessels, one of the Oerlikons was later replaced by a Bofors 40 mm gun.
Due to the variety of shipyards constructing the corvettes, as well as the varying roles Bathurst class ships were pressed into, there was no true standardisation of armament. Some ships varied significantly from the common armament profile. At one stage, HMAS Geraldton carried six Oerlikon cannons, a number later reduced to four. HMAS Junee only carried a single 4-inch gun and a single 40 mm anti-aircraft gun, possibly the lightest armament on a Bathurst class corvette.
The Bathurst's were equipped with modified Type 128 asdic equipment, redesigned to be used without a gyroscopic stabiliser.
Admiralty (later RAN)
The 56 corvettes commissioned as Australian vessels travelled a combined total of 6.7 million nautical miles (12.41 million kilometres, 7.71 million miles) during their service with the Royal Australian Navy.
A monument to the 56 Australian-operated corvettes is located at the Royal Australian Navy Heritage Centre, at Garden Island, Sydney. The monument, Corvettes, was unveiled by Rear Admiral Peter Sinclair on November 12 1995. Also at Garden Island, Sydney, a stained glass window listing the names of the corvettes frames the upper balcony doors of the Naval Chapel.