During the mid-1930s, the Australian Government upgraded its coastal defence batteries protecting the major ports of the country from enemy attack.

At Leighton, Swanbourne, North Mole, Fremantle Harbour, South Beach and Point Peron, the batteries were upgraded.

The Fort Forrest guns were moved to Swanbourne in 1935, with Buckland Hill, the future Leighton Battery, not selected at this point because of its proximity to vital other installations.

At the start of World War II, both of the batteries at Rottnest Island and the Arthur Head and Swanbourne ones were operational.

[1] In 1983 the National Trust of Western Australia documented the extent of the Fremantle Fixed Defences Coast Artillery Batteries as at 1943.

J Battery is a significant element in the surviving fabric of the Second World War coastal defences of Cockburn Sound and Fremantle.

Two US-supplied mobile Canon de 155 mm guns on Panama mount were installed to protect Garden Island, Cockburn Sound and the Challenger Passage.

Also the detail fabric of the Battery including gun mountings, reinforced concrete, brick and the double wall system.

[1] This Wikipedia article was originally based on J Gun Battery, entry number 105272 in the Australian Heritage Database published by the Commonwealth of Australia 2020 under CC-BY 4.0 licence, accessed on 4 January 2020.