13. Military jurisdiction is of two kinds: first, that which is conferred and defined by statute; second, that which is derived from the common law of war. Military offenses under the statute law must be tried in the manner therein directed; but military offenses which do not come within the statute must be tried and punished under the common law of war. The character of the courts which exercise these jurisdictions depends upon the local laws of each particular country. In the armies of the United States the first is exercised by courts-martial, while cases which do not come within the "Rules and Articles of War," or the jurisdiction conferred by a statute on courts-martial are tried by military commissions.
14. Military necessity as understood by modern civilized nations consists in the necessity o those measures which are indispensable ford securing the ends of the war and which are lawful according to the modern law and usages of war.
15. Military necessity admits of all direct destruction of life or limb of armed enemies and of other persons whose destruction is incidentally unavoidable in the armed contests of the war; it allows of the capturing of every armed enemy and every enemy of importance to the hostile Government or of peculiar danger to the captor; it allows of all destruction of property and obstruction of the ways and channels of traffic, travel or communication and of all withholding of sustenance or means of life from the enemy; of the appropriation of whatever an enemy's country affords necessary for the subsistence and safety of the army and of such deception as does not involve the breaking of good faith either positively pledged regarding agreements entered into during the war or supposed by the modern laws of war to exist. Men wh take up arms against one another in public war do not cease on this account to be moral beings responsible to one another and to God.
16. Military necessity does not admit of cruelty; that is infliction of suffering for the sake of suffering or for revenge, nor of maiming or wounding except in fight, nor of torture to extort confessions. It does not admit of the use of poison in any way, nor of the wanton devastation of a district. It admits of deception but disclaims acts of perfidy; and in general military necessity does not include any act of hostility which makes the return to peace unnecessarily difficult.
17. War is not carried on by arms alone. It is lawful to starve the hostile belligerent, armed or unarmed, so that it leads to the speedier subjection of the enemy.
18. When the commander of a besieged place expels the non-combatants in order to lessen the number of those who consume his stock of provisions it is lawful though an extreme measure to drive them back so as to hasten on the surrender.
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26. Commanding generals may cause the magistrates and civil officers of the hostile country to take the oath of temporary allegiance or an oath of fidelity to their own victorious Government or rulers and they may expel every one who declines to do so. But whether they do so or not the people and their civil officers owe strict obedience to them as long as they hold sway over the district or country at the peril of their lives.
27. The law of war can no more wholly dispense with retaliation than can the law of nations of which it is a branch; yet civilized nations acknowledge retaliation as the sternest feature of war. A reckless enemy often leaves to his opponent no other means of securing himself against the repetition of barbarous outrage.