Conscription

Conscription, which is mandatory mass military service, served as an informal ancient tool. Service in war often was expected for men, whether as subjects of an aggressive empire, members of an embattled tribe, or citizens of a political community, such as the Greek city-states of Athens and Sparta. This form of military service differed greatly and varied over time. This most powerful empire, Rome, however, relied on a professional military.

Complex feudal rules governed military service in medieval Europe. Kings could call up troops, but often did not directly organize these forces. Men who were resident in free towns could be obligated to defend their communities when these cities were threatened, and even peasants sometimes were organized into local militias. In addition, soldiers could be impressed. ...