Final answer:
The President of the United States is primarily responsible for the oversight and discipline of the entire command of the U.S. armed forces, as the Commander in Chief.
Step-by-step explanation:
The individual who is primarily responsible for the organization, performance of duty, and good order and discipline of the entire command within the U.S. armed forces is the President. According to Section 2 of the U.S. Constitution, the President holds the position of Commander in Chief of the Army and Navy, as well as the militia of the several states when in service. This role encompasses the oversight of the many elements including the Army, Navy, Marine Corps, and Air Force, and extends to matters such as training, deployment, and maintaining military discipline. Training and discipline are central to the effectiveness of military forces, as emphasized in historical texts, suggesting that a well-disciplined army results from the enforcement of commands during training. The President, as commander in chief, also has additional powers such as requiring opinions from executive department officers and granting reprieves and pardons for offenses against the United States, except in cases of impeachment.