The Constitution does not permit this government to prosecute a war as an uncivilized and barbarous people. As war is required by the frame-work of our government to be prosecuted according to the known usages of war among the civilized nations of the earth, it is important to understand what are the obligations, duties, and responsibilities imposed by war upon the military. Congress, not having defined, as under the Constitution it might have done, the laws of war, we must look to the usage of nations to ascertain the powers conferred in war, on whom the exercise of these powers devolve, over whom, and to what extent do these powers reach, and in how far the citizen and the soldier are bound by the legitimate use thereof. The power conferred by war is, of course, adequate to the end to be accomplished, and not greater than what is necessary to be accomplished. The law of war, like every other code of laws, declares what shall not be done, and does not say what may be done. The legitimate use of the great power of war, or rather the prohibitions upon the use of that power, increase or diminish as the necessity of the case demands. When a city is besieged and hard pressed the commander may exert an authority over the non-combatants which he may not when no enemy is near. All wars against a domestic enemy, or to repel invasions, are prosecuted to preserve the government. If the invading force can be overcome by the ordinary civil police of a country, it should be done without bringing upon the country the terrible scourge of war; if a commotion or insurrection can be put down by the ordinary process of law, the military should not be called out. A defensive foreign war is declared and carried on because the civil police is inadequate to repel it; a civil war is waged because the laws cannot be peacefully enforced by the ordinary tribunals of the country through civil process and by civil officers. Because of the utter inability to keep the peace and maintain order by customary officers and agencies in time of peace, armies are organized and put into the field. They are called out and invested with the powers of war to prevent total anarchy and to preserve the government.