The history of the Australian Army can be divided into two periods:
1901–1947, when limits were set on the size of the regular army, the vast majority of peacetime soldiers were in reserve units of the Citizens Military Force (also known as the CMF or Militia), and Australian Imperial Forces were formed to serve overseas, and Post-1947, when a standing peacetime regular infantry force was formed and the CMF (known as the Army Reserve after 1980) began to decline in importance.

During its history the Australian Army has fought a large number of major wars, including: Second Boer War (1899–1902), First World War (1914–1918), the Second World War (1939–1945), Korea War (1950–1953), Malayan Emergency (1950–1960), Indonesia-Malaysia Confrontation (1962–1966), Vietnam War (1962–1973) and more recently in Afghanistan (2001 – present) and Iraq (2003–2009). However, since 1947 it has also been involved in many peacekeeping operations, usually under the auspices of the United Nations. The largest one began in 1999 in East Timor. Other notable operations include peacekeeping on Bougainville and in the Solomon Islands, which are still ongoing to this day. Humanitarian relief after 2004 Indian Ocean earthquake in Aceh Province, Indonesia, Operation Sumatra Assist, ended on 24 March 2005.