The army has always been made up of constituent parts ranging from the section to corps and beyond. In hierarchical terms, an army looks as follows:The basic building block of an army is the section consisting of 10 men and an NCO. Three sections make a platoon, commanded by a lieutenant. Three rifle platoons and a small headquarters form a company, generally a major's command. Four rifle companies, a headquarters and internal support elements make up a battalion, commanded by a lieutenant-colonel. This is a unit; its component parts are sub-units. A brigade consists of three battalions, with attached supporting arms, commanded by a brigadier. A division (the lowest level of formation) comprises three brigades, and is commanded by a major-general. A corps consists of two or more divisions, and is a lieutenant-general's command. Two corps, at least, may be grouped to form an army.
From The Oxford Companion to Australian Military History in Oxford Reference.
Subjects: Military History.