•  Newcastle, NSW. September 1916. Group portrait of buglers of the 15th and 16th Infantry (Newcastle Battalion) Broadmeadow Camp. 

    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
    Army sub-units and units by corps
    Infantry Division: 1916
    Infantry Division: 1941

    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

    Formations consist of a variety of different corps units in addition to the infantry. The different structures of these other units are shown below. The sub-units are listed in ascending order.

    Army sub-units and units by corps

     
    Corps
    Sub-Unit & commander
    Unit & commander
    Army Service Corps
    Engineers
    Infantry
    Intelligence
    Military Police
    Ordnance
    Section (Sect) Corporal Battalion (Bn) Lieutenant Colonel
    Platoon (Pl) Lieutenant
    Company (Coy) Captain or Major
    Aviation
    Cavalry/Armour
    Engineers (post-1945)
    Signals
    Transport
    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.

    Infantry Division: 1916

    Infantry Division: 1941