The gathering of the (French) king's vassals for war; the whole body of vassals so assembled, or liable to be summoned; originally, the same as arrière-ban: in the 16th c., French usage created a distinction between ban and arrière-ban, for which see the latter word.
France was at such a Pinch..that they call'd their Ban and Arriere Ban, the assembling whereof had been long discussed, and in a manner antiquated.