Until Australia became a Federation in 1901, each of the six colonies were responsible for their own defence. From 1788 until 1870 this was done with British regular forces. In all, 24 British infantry regiments served in the Australian colonies. Each of the Australian colonies gained responsible government between 1855 and 1890, and while the Colonial Office in London retained control of some affairs, and the colonies were still firmly within the British Empire, the Governors of the Australian colonies were required to raise their own colonial militia. To do this, the colonial Governors had the authority from the British crown to raise military and naval forces. Initially these were militias in support of British regulars, but British military support for the colonies ended in 1870, and the colonies assumed their own defence. The separate colonies maintained control over their respective militia forces and navies until 1 March 1901, when the colonial forces were all amalgamated into the Commonwealth Forces following the creation of the Commonwealth of Australia. Colonial forces, including home raised units, saw action in many of the conflicts of the British Empire during the 19th century. Members from British regiments stationed in Australia saw action in India, Afghanistan, the New Zealand Wars, the Sudan conflict, and the Boer War in South Africa.

The Australian Army is the principal land warfare force of Australia, a part of the Australian Defence Force (ADF) along with the Royal Australian Navy and the Royal Australian Air Force. The Army is commanded by the Chief of Army (CA), who is subordinate to the Chief of the Defence Force (CDF) who commands the ADF. The CA is also directly responsible to the Minister for Defence, with the Department of Defence administering the ADF and the Army.