Capability development, which is often referred to as the military 'strength', is arguably one of the most complex activities known to humanity; because it requires determining: strategic, operational, and tactical capability requirements to counter the identified threats; strategic, operational, and tactical doctrines by which the acquired capabilities will be used; identifying concepts, methods, and systems involved in executing the doctrines; creating design specifications for the manufacturers who would produce these in adequate quantity and quality for their use in combat; purchase the concepts, methods, and systems; create a forces structure that would use the concepts, methods, and systems most effectively and efficiently; integrate these concepts, methods, and systems into the force structure by providing military education, training, and practice that preferably resembles combat environment of intended use; create military logistics systems to allow continued and uninterrupted performance of military organisations under combat conditions, including provision of health services to the personnel, and maintenance for the equipment; the services to assist recovery of wounded personnel, and repair of damaged equipment; and finally, post-conflict demobilisation, and disposal of war stocks surplus to peacetime requirements.
To coordinate military strategy with political affairs, the President has a National Security Council headed by the National Security Advisor. The collective body has only advisory power to the President, but several of the members who statutorily comprise the council (the Secretary of State, the Secretary of Energy and the Secretary of Defense) possess executive authority over their own departments.
From the time of its inception, the U.S. Armed Forces played a decisive role in the history of the United States. A sense of national unity and identity was forged as a result of victory in the First Barbary War and the Second Barbary War. Even so, the founders of the United States were suspicious of a permanent military force. It played a critical role in the American Civil War, continuing to serve as the armed forces of the United States, although a number of its officers resigned to join the military of the Confederate States. The National Security Act of 1947, adopted following World War II and during the Cold War's onset, created the modern U.S. military framework. The Act established the National Military Establishment, headed by the Secretary of Defense; and created the Department of the Air Force and the National Security Council. It was amended in 1949, renaming the National Military Establishment the Department of Defense, and merged the cabinet-level Department of the Army, Department of the Navy, and Department of the Air Force, into the Department of Defense.
The IRT model underlying ASVAB scoring is the three-parameter logistic (3PL) model. The 3PL model represents the probability that an examinee at a given level of ability will respond correctly to an individual item with given characteristics. Specifically, the item characteristics represented in the 3PL model are difficulty, discrimination (i.e., how well the item discriminates among examinees of differing levels of ability), and guessing (i.e., the likelihood that a very low ability examinee would respond correctly simply by guessing).