Royal Commission Appointed to Enquire into the Defence of British Possessions and Commerce Abroad 1879 to 1883 under the Earl of Carnarvon, designated Perth as a Defended Commercial Port. The main port was located at the mouth of the Swan River, Fremantle. A single coastal defence battery was built here at Arthurs Head in 1906.
During World War 2 a number of batteries were built to protect Fremantle. For a list of the World War 2 Batteries see here.