Armies are called out and organized to meet and overcome the active acting public enemies. But enemies with which armies have to deal are of two classes. 1. Open, active participants in hostilities, as soldiers who wear the uniform, move under the flag, and hold the appropriate commission from their government, openly assuming to discharge the duties and meet the responsibilities and dangers of soldiers, they are entitled to all belligerent rights, and should receive all the courtesies due to soldiers. The true soldier is proud to acknowledge and respect those rights, and ever cheerfully extends these courtesies. 2. Secret, but active participants, as spies, brigands, bushwhackers, jayhawkers, war-rebels, and assassins. In all wars, and especially civil wars, such secret, active enemies rise up to annoy and attack an army, and must be met and put down by the army. When lawless wretches become so impudent and powerful as not to be controlled and governed by the ordinary tribunals of a country, armies are called out and the laws of war invoked. War has never been and can never be conducted on the principle that an army is but a _posse comitatus_ of a civil magistrate. An army, like all other organized bodies, has a right, and its first duty is to protect its own existence, and the existence of all its parts, by the means and in the mode usual among civilized nations when at war. The question arises, then, do the laws of war authorize a different mode of proceeding and the use of different means against secret active enemies from those used against open active enemies? As has been said, the open enemy or soldier in time of war may be met in battle and killed, wounded, or taken prisoner, or so placed by the lawful strategy of war as that he is powerless. Unless the law of self-preservation absolutely demands it, the life of a wounded enemy or a prisoner must be spared.