" ... in pre-industrial times the army was as much an instrument for the maintenance of internal order as for defence against outsiders.
Indeed, the very distinction between internal and external warfare might be tenuous. Numerous states in history have consisted of a core area and a periphery, the former being subject to both military and administrative control, the latter to military control alone, so that regular displays of military superiority were required to keep the periphery within the fold [...] Few pre-industrial states had fixed borders, as opposed to vague frontier areas under the sway of local magnates, tribal groups, bandits or other unruly elements. "

― Patricia Crone , Pre-Industrial Societies: Anatomy of the Pre-Modern World