But once authorized, or the authorization renewed by renewed appropriations, congress is almost invariably wise enough to refrain from further interference. The art of war is recognized as a metier, a trade, the most exacting and absorbing of professions, demanding not only high technical skill, but for the utmost efficiency power completely within itself, the capacity to act as a unit. So governing the regular force is left to those competent from training and experience to guide it. Watched by a civilian secretary of war, the elements in control are the acts of congress, the articles-of-war, the rules and regulations of the service, and the individual authority, strictly limited and defined, of the officers from the chief-of-staff to the subalterns. The office of a man in commission is for life or during "good behavior"; ordinarily he can be removed only upon specific charges, and these must be proved before a duly constituted court-martial; in any event he may claim the protection of congress. But always these salient facts stand out unqualified—the entire separation of the civil from the military functions—the just jealousy and dominance of the civil power, the freedom within limits of the military, and also the clear line of demarcation between the legislative and judicial functions and those purely and properly executive.
The police force of the city of New York has some points of resemblance to the regular army, and many more where the analogy has no application. A policeman is in fact in hardly any sense a soldier; he is better to be described as a civilian, suitably armed, and clothed with powers and responsibilities relating primarily to the preservation of the peace, and incidentally to the detection of crime, the capture of criminals, the enforcement of the law and the arrest of violators of the law. This force, unlike the army, is the creation almost of yesterday; principles virtually settled as to the national body of armed men, have not as yet taken definite and coherent shape with them. The blundering incident to everything new, raw and tentative, may be traced in the numerous experiments made in compliance with enactments of the state legislature. These have been due mainly to party policy, but sometimes to well-meant ignorance (often miscalled "reform") and sometimes, it is to be feared, to deliberate or even immoral scheming. Sometimes a board of commissioners, all of one party, has controlled the department; sometimes—as at present—a single head, and at one time (1895-97) a so-called bi-partizan board, divided nominally equally between democrats and republicans, was in power. Not even the extraordinary ability of Mr. Roosevelt, chairman of the board, could overcome the obstacle of divided responsibility. He left at least one good trace of his incumbency, the tenacity with which he held to the important doctrine that it was not the province of a commissioner to criticize the laws under which he acted, but to enforce them.