The best analogy to explain the structure of the Army is a collection of building blocks called sub-units that are combined in different ways to form larger groups that are known as units. Different combinations of these units can in turn be put together to form larger groups, known as formations. The basic structure of the Army is outlined below:
Basic Army structure
Formations Organisation Strength Made up of Commanded by Army Two or more corps General Corps 30,000 or more Two or more divisions Lieutenant General Division 10,000 - 20,000 3 brigades Major General Brigade 2,500 - 5,000 WWI WWII Brigadier (General) 4 battalions 3 battalions (sub-) units Battalion 550 - 1000 4 companies 4 companies Lieutenant Colonel Company 100 - 225 4 platoons 3 platoons Captain or Major Platoon 30 - 60 4 (later 3) sections 3 sections Lieutenant Section 9 - 16 Corporal/Sergeant
Army sub-units and units by corpsCorpsSub-Unit & commanderUnit & commander
Army Service Corps
Section (Sect) Corporal Battalion (Bn) Lieutenant Colonel Platoon (Pl) Lieutenant Company (Coy) Captain or Major Aviation
Section (Sect) Corporal Regiment (Regt) Lieutenant Colonel Troop (Tp) Lieutenant Squadron (Sqn) Captain or Major Artillery (pre-1939) Detachment (Det) Sergeant Brigade (Bde) Lieutenant Colonel Section (Sect) Lieutenant Battery (Bty) Major Artillery (post-1939) Detachment (Det) Sergeant Regiment (Regt) Lieutenant Colonel Section (Sect) Lieutenant Troop (Tp) Lieutenant/Captain Battery (Bty) Major
Australia has only fought with forces larger than a brigade in the two world wars. The diagrams below roughly illustrate the organisation of an Australian infantry division in 1916 and in 1941.