The history of Australian security during the twentieth century is told largely in accounts of Australia in world affairs, and often in simplified form. According to successive governments, Australian security challenges have arisen from the tension between geography (an island continent in the South Pacific) and history (of British settlement and predominance in shaping institutions and identity). In exploring Australian military preparation and planning, involvement in wars, the protests that resulted and Australia's foreign policies more generally, the more probing interpretations go beyond the conventional tension between geography and history.

This chapter deals principally with Australia in world affairs, but examines connections between internal and external threats. It is also sensitive to the tension between a global Australian outlook, owing much to European and then Anglo-American thinking, and a form of provincialism that certainly derived from geography but also from the circumstances of Australia's continental Federation. European thought is both indispensable and inadequate in thinking through the political and historical circumstances of formerly colonised states such as India. There is also something indispensable and yet inadequate about what has, in recent years, been called ‘the British World’ – the empire formed by British settlement and the extension of British values – as the lens through which to view all Australian security fears and reactions. Similarly, although deployed often and casually by politicians, the concept of security involves more than protection against foreign enemies: studies of security require exploration of connections between internal and external threats; and they suggest that, as security links closely to identity, it necessarily includes and excludes groups of people in its articulation.

The history of Australia's search for security divides logically into the two halves of the twentieth century. Up to the mid-1950s participation in world wars as part of the British Empire shaped Australians' global outlook. This was accompanied by a preference for a citizen soldiery rather than large professional forces, and an expeditionary mentality.