Established during World War II to advise the President regarding the strategic direction of the armed forces of the United States, the Joint Chiefs of Staff (JCS) continued in existence after the war and, as military advisers and planners, have playeda significant role in the development of national policy. Knowledge of JCS relations with the President, the National Security Council, and the Secretary of Defense in the years since World War II is essential to an understanding of their current work. An account of their activity in peacetime and during times of crisis provides, moreover, an important series of chapters in the military history of the United States. For these reasons, the Joint Chiefs of Staff directed that an official history be written for the record. Its value for instructional purposes, for the orientation of officers newly assigned to the JCS organization and as a source of information for staff studies, will be readily recognized.