Lieber Code of 1863: Section VIII
135. An armistice is the cessation of active hostilities for a period agreed between belligerents. It must be agreed upon in writing and duly ratified by the highest authorities of the contending parties.
136. If an armistice be declared without conditions it extends no further than to require a total cessation of hostilities along the front of both belligerents.
If conditions be agreed upon, they should be clearly expressed, and must be rigidly adhered to by both parties. If either party violates any express condition, the armistice may be declared null and void by the other.
137. An armistice may be general, and valid for all points and lines of the belligerents; or special–that is, referring to certain troops or certain localities only. An armistice may be concluded for a definite time; or for an indefinite time, during which either belligerent may resume hostilities on giving the notice agreed upon to the other.
138. The motives which induce the one or the other belligerent to conclude an armistice, whether it be expected to be preliminary to a treaty of peace, or to prepare during the armistice for a more vigorous prosecution of the war, does in no way affect the character of the armistice itself.
139. An armistice is binding upon the belligerents from the day of the agreed commencement; but the officers of the armies are responsible from the day only when they receive official information of its existence.
140. Commanding officers have the right to conclude armistices binding on the district over which their command extends, but such armistice is subject to the ratification of the superior authority, and ceases so soon as it is made known to the enemy that the armistice is not ratified, even if a certain time for the elapsing between giving notice of cessation and the resumption of hostilities should have been stipulated for.
141. It is incumbent upon the contracting parties of an armistice to stipulate what intercourse of persons or traffic between the inhabitants of the territories occupied by the hostile armies shall be allowed, if any.
If nothing is stipulated the intercourse remains suspended, as during actual hostilities.
142. An armistice is not a partial or a temporary peace; it is only the suspension of military operations to the extent agreed upon by the parties.
143. When an armistice is concluded between a fortified place and the army besieging it, it is agreed by all the authorities on this subject that the besieger must cease all extension, perfection, or advance of his attacking works as much so as from attacks by main force.
But as there is a difference of opinion among martial jurists whether the besieged have a right to repair breaches or to erect new works of defense within the place during an armistice, this point should be determined by express agreement between the parties.
144. So soon as a capitulation is signed the capitulator has no right to demolish, destroy, or injure the works, arms, stores, or ammunition in his possession, during the time which elapses between the signing and the execution of the capitulation, unless otherwise stipulated in the same.
145. When an armistice is clearly broken by one of the parties the other party is released from all obligation to observe it.
146. Prisoners taken in the act of breaking an armistice must be treated as prisoners of war, the officer alone being responsible who gives the order for such a violation of an armistice. The highest authority of the belligerent aggrieved may demand redress for the infraction of an armistice.
147. Belligerents sometimes conclude an armistice while their plenipotentiaries are met to discuss the conditions of a treaty of peace; but plenipotentiaries may meet without a preliminary armistice; in the latter case the war is carried on without any abatement.