By military department, $146.9 billion was allocated for the Department of the Army, $168.8 billion for the Department of the Navy, $161.8 billion for the Department of the Air Force and $102.8 billion for DoD-wide spending.[4] By function, $138.6 billion was requested for personnel, $244.4 billion for operations and maintenance, $118.9 billion for procurement, $69.0 billion for research and development, $1.3 billion for revolving and management funds, $6.9 billion for military construction and $1.3 billion for family housing.[4]

Somewhat earlier, in medieval China, gunpowder had been invented, and was increasingly used by the military in combat. The use of gunpowder in the early vase-like mortars in Europe, and advanced versions of the long bow and cross bow, which all had armour-piercing arrowheads, that put an end to the dominance of the armoured knight. After the long bow, which required great skill and strength to use, the next most significant technological advance was the musket, which could be used effectively, with little training. In time, the successors to muskets and cannon, in the form of rifles and artillery, would become core battlefield technology.
The primary reason for the existence of the military is to engage in combat, should it be required to do so by the national defence policy, and to win. This represents an organisational goal of any military, and the primary focus for military thought through military history. How victory is achieved, and what shape it assumes, is studied by most, if not all, military groups on three levels.
As in most militaries, members of the U.S. Armed Forces hold a rank, either that of officer, warrant officer or enlisted, to determine seniority and eligibility for promotion. Those who have served are known as veterans. Rank names may be different between services, but they are matched to each other by their corresponding paygrade.[21] Officers who hold the same rank or paygrade are distinguished by their date of rank to determine seniority, while officers who serve in certain positions of office of importance set by law, outrank all other officers in active duty of the same rank and paygrade, regardless of their date of rank.[22] In 2012, it was reported that only one in four persons in the United States of the proper age meet the moral, academic and physical standards for military service.[23]

After enlistment, new recruits undergo basic training (also known as "boot camp" in the Marine Corps, Navy and Coast Guard), followed by schooling in their primary Military Occupational Specialty (MOS), rating and Air Force Specialty Code (AFSC) at any of the numerous training facilities around the United States. Each branch conducts basic training differently. The Marine Corps send all non-infantry MOS's to an infantry skills course known as Marine Combat Training prior to their technical schools. Air Force Basic Military Training graduates attend Technical Training and are awarded their Air Force Specialty Code (AFSC) at the apprentice (3) skill level. All Army recruits undergo Basic Combat Training (BCT), followed by Advanced Individual Training (AIT), with the exceptions of cavalry scouts, infantry, armor, combat engineers and military police recruits who go to One Station Unit Training (OSUT), which combines BCT and AIT. The Navy sends its recruits to Recruit Training and then to "A" schools to earn a rating. The Coast Guard's recruits attend basic training and follow with an "A" school to earn a rating.

In 1974, the first six women naval aviators earned their wings as Navy pilots. The Congressionally mandated prohibition on women in combat places limitations on the pilots' advancement,[34] but at least two retired as captains.[35] In 1989, Captain Linda L. Bray, 29, became the first woman to command American soldiers in battle during the invasion of Panama. The 1991 Gulf War proved to be the pivotal time for the role of women in the U.S. Armed Forces to come to the attention of the world media; there are many reports of women engaging enemy forces during the conflict.[36]
Although concerned with research into military psychology, and particularly combat stress, and how it affect troop morale, often the bulk of military science activities is directed at military intelligence technology, military communications, and improving military capability through research. The design, development, and prototyping of weapons, military support equipment, and military technology in general, is also an area in which lots of effort is invested – it includes everything from global communication networks and aircraft carriers to paint and food.

Just as the President, the Secretary of Defense, and the Secretary of Homeland Security, are in charge of the entire military establishment, maintaining civilian control of the military, so too are each of the Defense Department's constitutive military departments headed by civilians. The four DoD branches are organized into three departments, each with civilian heads. The Department of the Army is headed by the Secretary of the Army, the Department of the Navy is headed by the Secretary of the Navy and the Department of the Air Force is headed by the Secretary of the Air Force. The Marine Corps is organized under the Department of the Navy, however it is still considered a separate and equal service. The Coast Guard is under the Department of Homeland Security and receives its operational orders from the Secretary of Homeland Security. However, the Coast Guard may be transferred to the Department of the Navy by the President or Congress during a time of war, thereby placing it within the DoD.[17]


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.[16]

Military history is often considered to be the history of all conflicts, not just the history of the state militaries. It differs somewhat from the history of war, with military history focusing on the people and institutions of war-making, while the history of war focuses on the evolution of war itself in the face of changing technology, governments, and geography.
Although concerned with research into military psychology, and particularly combat stress, and how it affect troop morale, often the bulk of military science activities is directed at military intelligence technology, military communications, and improving military capability through research. The design, development, and prototyping of weapons, military support equipment, and military technology in general, is also an area in which lots of effort is invested – it includes everything from global communication networks and aircraft carriers to paint and food.
After the final ability estimate is computed, it is converted to a standard score on the ASVAB score scale that has been statistically linked to the ability estimate through a process called equating. Equating studies are conducted for every paper and pencil ASVAB form to ensure that scores have the same meaning regardless of which test form the examinee receives.
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