In modern, professionalized armies, command structures tend to be composed of units and subunits, and the chain of command goes from commanding officer of a superior unit to the commanding officer of subordinate unit.

Please note, that I am not asking about whether military forces were always composed of separate units, but the history of a chain of command built around units instead of officers (or other type of leader). In the current U.S. Army, for example, it's not quite the case that a First Lieutenant reports to a Captain. The commanding officer of a specialty platoon reports to the commanding officer of a company. The commanding officers of a specialty platoon and a company are typically a First Lieutenant and a Captain, but if these officers are incapacitated in battle, the next highest ranking officer takes the role of commanding officer.

What is the history of this form of organization? This seems quite different, than say, feudalism, where knights were personal followers of their generals. If a knight fell, his vassals would not necessarily keep operating as a unit.

Book suggestions on this topic are very welcome. Huntington's Soldier and the State and Preston's Men in Arms look very relevant.

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    This is essentially asking for the history of the professional army. Even in antiquity, the professional armies were sub-divided into units and sub-units because that was the only way to manage so many men. Mar 15, 2017 at 21:15
  • yes, I think it probably is the history of the standing, professional army. Any canonical books on that subject?
    – fgregg
    Mar 15, 2017 at 21:26
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    @KillingTime It could also be an evolution from very small tribes. A tribe chief subjugates 10 other tribes, one after the other. Now he has an army - he tells each of the 10 tribes' chiefs what to do, and they tell their small group of warriors.
    – SPavel
    Mar 15, 2017 at 21:32
  • @SPavel While most modern infantry is divided into sections/squads of 4-10 men at the smallest level, this was only really formalised towards the end of WWI - for a couple of hundred years before then, the 25-30 man platoon was about the smallest grouping, and most formations were company-sized (90-120 men).
    – user13123
    Mar 16, 2017 at 1:01
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    I don't understand the edit which says "the history of a chain of command built around units instead of officers" - chain of command (almost by definition) requires a leader at each level down to the smallest unit. The Roman army had the equivalent of both commissioned and non-commissioned officers in its ranks, so the concept isn't modern. Mar 20, 2017 at 22:35

1 Answer 1


All large enough armies have to be organized on this hierarchic principle. Otherwise one will have not an army but a disorganized crowd which is impossible to control. All that we know about ancient armies shows that they were organized like this, another matter is that we do not know many details about some of them. The best known example is the Roman army which consisted of legions, centuriae and manipulae. Mongol army in the Middle age was organized by strictly decimal principle, at least in theory, into tens, hundreds, thousands and tens of thousands. In much smaller European feudal armies, each lord has his unit which obeyed him, and the lords of the units obeyed (in principle) the chief commander. So there were at least two steps of the hierarchic structure.

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