Structure of the Australian Army during World War I
The structure of the Australian Army during World War I included a small force of mostly militia which served in Australia and larger expeditionary forces which were raised for deployment overseas following the outbreak of the conflict in August 1914. The home army consisted of the small regular Permanent Forces, the part-time Citizen Forces, and the Australian Garrison Artillery, which were maintained in Australia to defend the country from attack, while expeditionary forces consisted of the Australian Naval and Military Expeditionary Force which occupied German New Guinea from September 1914, and the Australian Imperial Force which fought at Gallipoli in 1915, and in the Middle East and on the Western Front in Europe from 1916 to 1918. Following an initial precautionary mobilisation following the outbreak of war, by the end of August 1914 those units of the reserve formations of the home army that had been activated began to stand down. From 1915, only skeleton garrisons were maintained at coastal forts. Meanwhile, as the war continued overseas the AIF sustained heavy losses, and although it expanded considerably during the war, with the voluntary recruitment system unable to replace its casualties by 1918 most of its units were significantly undermanned.
Divisions
During the war, Australia raised an all volunteer force for overseas service, known as the Australian Imperial Force, which subsequently served in several theatres, including the Gallipoli Campaign, the Sinai and Palestine Campaign and on the Western Front in France and Belgium. Between the start of the war in August 1914 and its end in November 1918, Australia raised a total of seven infantry divisions, one of which - the New Zealand and Australian Division - was also manned by New Zealanders. Of these, six took part in combat, while one - the 6th - was broken up in the United Kingdom and disbanded in September 1917 before being deployed due to manpower shortages. In addition, there were two mounted divisions raised: the ANZAC Mounted Division and the Australian Mounted Division.| Designation | Date raised | Date disbanded | Campaigns | Notes |
| Australian 1st Division | 1914 | 1919 | Gallipoli and the Western Front | |
| Australian 2nd Division | 1915 | 1919 | Gallipoli and the Western Front | |
| Australian 3rd Division | 1916 | 1919 | Western Front | |
| Australian 4th Division | 1916 | 1919 | Western Front | |
| Australian 5th Division | 1916 | 1919 | Western Front | |
| Australian 6th Division | 1917 | 1917 | Broken up before being deployed | |
| New Zealand and Australian Division | 1915 | 1915 | Gallipoli | |
| ANZAC Mounted Division | 1916 | 1919 | Sinai and Palestine Campaign | |
| Australian Mounted Division | 1917 | 1919 | Sinai and Palestine Campaign |