Fremantle Fortress

The first coastal defences to be installed in Western Australia were at Albany in 1893; the Fremantle ones were only established after the opening of the inner harbour in 1897. The coastal protection of Fremantle Harbour was established in 1906, when two 6-inch Mk VII naval guns were installed at Fort Arthur Head, which eventually became the Arthurs Battery. In 1911, the decision was made to build a major naval base south of Fremantle, the Henderson Naval Base, with construction starting in 1913. The project came to a halt during World War I and was abandoned in 1920 for financial and strategic reasons. During the mid-1930s, the Australian Government upgraded its coastal defence batteries protecting the major ports of the country from enemy attack. In Western Australia, protection of Fremantle Port was a priority. This was to be achieved by upgrading existing batteries and constructing new ones. At Buckland Hill, Swanbourne, North Mole, Arthur Head, South Beach, Point Peron, Garden Island and Rottnest Island, batteries were either upgraded or new batteries were to be installed. These combined coastal defences were referred to as the Fremantle Fortress. Originally, the defence of the port was to be achieved through the placement of 9.2-inch naval guns at Buckland Hill but this was deemed insufficient to protect the port from long-range bombardment by cruisers equipped with 8-inch guns. Instead, the 9.2-inch guns were placed on Rottnest Island as part of the Oliver Hill Battery, which allowed engagement of enemy ships before they reached a range where they could fire at Fremantle Port, The defence of Fremantle Port was deemed essential to national Australian security during a potential future war. ==Batteries==

The island-based batteries that made up the Fremantle Fortress during World War II were the Oliver Hill and Bickley Batteries on Rottnest Island, and the Challenger, Beacon and Scriven Batteries on Garden Island. On the mainland, from north to south, the Swanbourne, Leighton, Harbour, Arthurs and Peron Batteries made up the Fremantle Harbour defence. The Rottnest Island Oliver Hill Battery was tasked with the long-range protection of the port while the Garden Island and Peron batteries mainly served to protect the anchorage in Cockburn Sound. Additionally, secondary batteries existed in the form of Collie, located on Garden Island, and the secondary armament at Peron. In post-war Australia, the battery was used for training purposes by the army and, from 1952, by the Citizens’ Military Force. Usage of the battery ceased in 1963 and the entrances to the tunnels were closed off. ==Anti-submarine boom nets==

To protect the Fremantle Harbour, anti-submarine and anti-torpedo boom nets were installed across the harbour entrance in 1941, spanning between North and South Moles. This barrier was a buoyed wire mesh net that could be opened in its centre by a winch at North Mole. Additionally, an indicator loop was laid between Rottnest Island and Swanbourne. To protect the anchorage at Cockburn Sound, a major engineering project was required. An almost 9.5 km long anti-submarine net in the shape of an arch spanned from the north-eastern end of Garden Island to Woodman Point, on the mainland. Construction of this barrier took from 1942 to 1944. From Woodman Point, the barrier ran west on top of the Parmelia Bank, a sandbank stretching to Carnac Island. A dredged channel, the location of a gate in the barrier, let through the sandbank into Cockburn Sound. From this channel, the barrier ran south-west to Garden Island. This Cockburn Sound barrier was in place until 1964, when the timber pylons and dolphins were demolished, using explosives. The steel nets were dropped onto the seabed by cutting them. Despite this, some remains of the old barrier are still visible, with a number of timber pylons still extending above the water line. Remnants of the old cable have also been found at Woodman Point. At the southern end, between Point Peron and Garden Island, a Type "A" anti-boat scaffolding, a so-called hurdle defence, was erected, roughly in the position of the modern Garden Island causeway and bridge. Construction of this barrier started in late 1943, and it was removed shortly after the war, finding civilian use by being recycled as building material for farm sheds. ==Post military-use==

The Commonwealth of Australia gave up the Buckland Hill site of Leighton Battery in 1984, handing it to the Town of Mosman Park. Most of it was redeveloped while other parts became a public reserve. The area previously occupied by the Leighton Battery was awarded to the Royal Australian Artillery Historical Society of Western Australia for the purpose of operating a museum at the site. The naval gun and shield were installed at Leighton Battery in September 2015 to replicate the original 6-inch guns at site. The Leighton Battery, on Buckland Hill, and its underground tunnels have been partially restored and are accessible. Tours of the underground tunnels at the site are held on Sundays. ==Heritage listings==

The site of the Leighton Battery was added to the now-defunct Register of the National Estate on 22 June 1993. National Trust Classification was awarded on 13 May 1996 and it was declared a State Register of Heritage Places on 27 August 1999. Nominated in June 2014, the site was awarded an Engineering Heritage National Marker by Engineers Australia in November 2014. The Rottnest Island component of the Fremantle Fortress was awarded an Engineering Heritage National Marker by Engineers Australia in November 2010. The Oliver Hill 9.2-inch battery is the last remaining one of the seven batteries of this type constructed in Australia and one of very few remaining in the world. The Challenger Battery was added to the Commonwealth Heritage List on 22 June 2004. == See also ==