5. The power to grant pardons for offenses against the laws of the United States. =Execution of the Laws.=--The President is the head of the executive branch of the government, and it is his duty to see that the Constitution is preserved, protected, and defended, and that the laws enacted in pursuance thereof, the treaties made under its authority, and the decisions rendered by the federal courts are enforced throughout the United States. For these purposes the army, the navy, and the militia are at his disposal, and in case of resistance to the laws and authority of the United States, they may be employed by him in such manner as he may direct, to overcome such resistance. Moreover, nearly all the civil and military officers of the United States are appointed by him and are, to a large degree, subject to his direction. _The President's Responsibility._--Unlike the state governments, the national government is so organized as to concentrate the power and the responsibility for the enforcement of the laws in the hands of a single executive. Those who are charged with aiding him in carrying out the government are his own appointees, and their responsibility is primarily to him alone. =Power of Appointment.=--The Constitution declares that the President shall, with the "advice and consent" of the senate, appoint all officers of the United States whose appointment is not otherwise provided for by the Constitution, except that Congress may vest the appointment of inferior officers in the President alone, in the courts of law, or in the heads of departments.[76] This is one of the most important powers devolving upon the President, and probably consumes more of his time than all his other duties together. In the early days of the Constitution, the number of appointments was small, but as the government service expanded, the number of offices to be filled steadily increased until there are now about 11,000 important presidential offices, that is, offices filled by the President and the senate. The tenure of office act of 1820 fixed the terms of the great bulk of federal offices at four years, and even where the term is not prescribed by statute, it is the custom for most appointees to be replaced at the expiration of four years, so that in practice the four-year tenure is universal, except for federal judges, and each President must during his term make appointments to nearly all the presidential offices. In making these appointments he is not limited by any constitutional or statutory requirements in regard to qualifications. He is the sole judge of the fitness of candidates for appointments. The only limitation upon his power is the necessity of securing the approval of the senate, a requirement already discussed in chapter x, pages 190-191.