arriere-ban

from The Century Dictionary.

• noun In the early feudal state, the summons of the sovereign to all freemen, calling them to the field with their vassals, equipment, and three months' provisions. Neglect to obey the summons brought fines or even loss of the fief. Hence The military force thus liable to be called out. Formerly written arierban.

from the GNU version of the Collaborative International Dictionary of English.

• noun A proclamation, as of the French kings, calling not only their immediate feudatories, but the vassals of these feudatories, to take the field for war; also, the body of vassals called or liable to be called to arms, as in ancient France.