Although the twentieth century is regarded as a century of global war, it left Australia remarkably unscathed. The colonial conquest of Aboriginal Australia had been largely completed and basic cultural survival within white society became a more pressing objective for indigenous people. Two world wars were fought mostly in other parts of the world, with only relatively minor air raids and submarine attacks having a direct impact on Australian soil. The ideological war between Communism and capitalism was fought to the north, but Australia was never a potential domino. One of the paradoxes of the Australian situation therefore is that despite the lack of a direct threat to the land during the past century Australians were so willing to volunteer to fight and die elsewhere. The resulting legacy of a century of war for archaeologists is primarily made up of war memorials (without cemeteries) and coastal defences that never fired in anger.
Presented herein is an overview of the archaeology of the coastal defence of Australia, focusing on Sydney, New South Wales. As the largest city and primary strategic port of Australia it has the most comprehensive collection of defences against enemy attack. The sites span the period from almost the start of European settlement in 1788 to the 1960s. Many have now been incorporated into the national park system that surrounds Sydney and are part of the recognized cultural heritage of the nation. The study of these remains has great potential to show the developing nature of Australia's responsibility for defence as a key aspect of its evolving independence from Britain, and to reveal how Australians saw that relationship. It also shows the way the paradox noted above informs our modern views about the archaeological remains.
The provision of defence is one of the defining purposes of nations, generally through a standing army and the safeguarding of borders. Imperial powers also project their national interest to supporting economic colonies or command of the sea or directly thwarting their opponents. The British Empire relied upon all three strategies to maintain its global position during the nineteenth century, with the Australian colonies firmly dependent upon Britain for much of that time.