A Slim Barrier: The Defence of Mainland Australia 1939-1945

Abstract

Two questions apply regarding Australia in World War II: what measures were taken to defend mainland Australia, and were those measures effective in meeting the perceived threat to Australia? Mainland Australia is defined as the mainland, Tasmania and the littoral waters out to 200 nautical miles (excluding New Guinea). Mainland defence is assessed at a systemic level, where the major elements of mainland defence are point defence systems, area defence systems, lines of communication, surveillance and intelligence. The minor elements are production capacity and national will. A qualitative assessment is made in each of six shifts in perceived threat. The fit for purpose test is applied: were the elements of mainland defence at that time appropriate to meet the perceived threat? The outcomes of the analysis follow. At the start of the European war the perceived threats were German attacks on shipping (minor scale) or, at a medium scale, sustained attack on shipping and concurrent heavy raids if a war started with Japan. Mainland defence was partially fit for purpose. When France fell and Italy declared war (mid-1940) there were three possible scales of Japanese attack: bombardment, light raids and invasion. Mainland defence was partially fit for purpose. After the start of the Pacific War, events moved rapidly in the first 100 days. Threats were seen as: air attack; naval bombardment; a sea-borne raid; attack to permanently occupy territory; and invasion of Australia. Mainland defence was not fit for purpose. When MacArthur arrived (March 1942) threats were: attacks in force against Australia, including invasion; attacks against Australian lines of communication. By then mainland defence was partially fit for purpose. During the ‘holding war’ (mid-1942 – mid-1943) the Government held that incursion could not be ruled out. However the services saw the threat as sea bombardment, torpedo attack and air attack. By now mainland defence was fit for purpose, with the exception of Anti-Submarine Warfare. Finally from mid-1943 to mid-1944 there was some residual threat. Mainland defence, despite being reduced, was fit for purpose. From mid-1944 on there was no threat, so the questions do not apply.