Unified Combatant Command in the context of "Chief of Staff of the United States Army"

The United States secretary of defense (SecDef), secondarily titled the secretary of war (SecWar), is the head of the United States Department of Defense (DoD), the executive department of the U.S. Armed Forces, and is a high-ranking member of the cabinet of the United States. The secretary of defense's position of command and authority over the military is second only to that of the president of the United States, who is the commander-in-chief. This position corresponds to what is generally known as a defense minister in many other countries. The president appoints the secretary of defense with the advice and consent of the Senate, and is by custom a member of the Cabinet and by law a member of the National Security Council.

Subject only to the orders of the president, the secretary of defense is in the chain of command and exercises command and control, for both operational and administrative purposes, over all DoD-administered service branches  – the Army, Marine Corps, Navy, Air Force, and Space Force – as well as the Coast Guard when its command and control is transferred to the Department of Defense. Only the secretary of defense (or the president or Congress) can authorize the transfer of operational control of forces between the three military departments (Department of the Army, the Navy, and the Air Force) and the eleven Unified Combatant Commands.

The Joint Chiefs of Staff (JCS) is the body of the most senior uniformed leaders within the United States Department of Defense, which advises the president of the United States, the secretary of defense, the Homeland Security Council and the National Security Council on military matters. The composition of the Joint Chiefs of Staff is defined by statute and consists of a chairman, a vice chairman, the chiefs of the Army, Marine Corps, Navy, Air Force, and Space Force, and the chief of the National Guard Bureau. Each of the individual service chiefs, outside their Joint Chiefs obligations, works directly under the secretaries of their respective military departments, e.g. the secretary of the Army, the secretary of the Navy, and the secretary of the Air Force.

Following the Goldwater–Nichols Act in 1986, the Joint Chiefs of Staff do not have operational command authority, either individually or collectively, as the chain of command goes from the president to the secretary of defense, and from the secretary to the regional combatant commanders. Goldwater–Nichols also created the office of vice chairman, and the chairman is now designated as the principal military adviser to the secretary of defense, the Homeland Security Council, the National Security Council and the president.

A Numbered Air Force (NAF) is a type of organization in the United States Air Force that is subordinate to a major command (MAJCOM) and has assigned to it operational units such as wings, squadrons, and groups. A Component Numbered Air Force (C-NAF) has the additional role as an Air Force Component Command exercising command and control over air and space forces supporting a Unified Combatant Command. Unlike MAJCOMs, which have a management role, a NAF is a tactical organization with an operational focus, and does not have the same functional staff as a MAJCOM. Numbered air forces are typically commanded by a major general or a lieutenant general.

Numeric designations for Numbered Air Forces are written in full using ordinal words (e.g., Eighth Air Force), while cardinal numerals are used in abbreviations (e.g., 8 AF). Units directly subordinate to a NAF were traditionally numbered 6XX (where XX is the NAF number). For example, the 609th Air Operations Center is a unit subordinate to the Ninth Air Force. This is no longer completely accurate, due to regular reorganization of Wings and Numbered Air Forces.

The Active Guard and Reserve (AGR) is a United States Army and United States Air Force federal military program which places Army National Guard and Army Reserve soldiers and Air National Guard and Air Force Reserve airmen on federal active duty status under Title 10 U.S.C., or full-time National Guard duty under Title 32 U.S.C. 502(f) for a period of 180 consecutive days or greater in order to provide full-time support to National Guard and Reserve organizations for the purpose of leading, organizing, administering, recruiting, instructing, or training the Reserve Components according to Subsection 101(d)(6). AGR personnel may also be assigned to active duty roles in support of Regular Army and Regular Air Force organizations or joint organizations such as the Office of the Secretary of Defense, Secretary of the Army, Secretary of the Air Force, the Joint Staff, or the Unified Combatant Commands.

The Goldwater–Nichols Department of Defense Reorganization Act of October 4, 1986 (Pub. L. 99–433; signed by President Ronald Reagan) made the most sweeping changes to the United States Department of Defense since the department was established in the National Security Act of 1947 by reworking the command structure of the U.S. military. It increased the powers of the chairman of the Joint Chiefs of Staff and implemented some of the suggestions from the Packard Commission, commissioned by President Reagan in 1985. Among other changes, Goldwater–Nichols streamlined the military chain of command, which now runs from the president through the secretary of defense directly to combatant commanders (CCDRs, all four-star generals or admirals), bypassing the service chiefs. The service chiefs were assigned to an advisory role to the president and the secretary of defense, and given the responsibility for training and equipping personnel for the unified combatant commands.

Named after Senator Barry Goldwater (R-Arizona) and Representative Bill Nichols (D-Alabama), the bill passed the House of Representatives, 383–27, and the Senate, 95–0. It was signed into law by President Reagan on October 1, 1986. Admiral William J. Crowe was the first chairman to serve under this new legislation.

Area of responsibility (AOR) is a pre-defined geographic region assigned to Combatant commanders of the Unified Command Plan (UCP), that are used to define an area with specific geographic boundaries where they have the authority to plan and conduct operations; for which a force, or component commander bears a certain responsibility. The term may also be used in other countries worldwide but it originated within the United States Armed Forces. This system is designed to allow a single commander to exercise command and control of all military forces in the AOR, regardless of their branch of service.

George W. Bush signed the U.S. Unified Command Plan (UCP) 2008 on 17 December 2008, establishing the up-to-date boundaries for the newest Command, United States Africa Command (USAFRICOM), and all changes to boundaries of the other Commands.

The United States Forces Korea (USFK) is a subordinate unified command of U.S. Indo-Pacific Command (USINDOPACOM). USFK was initially established in 1957, and encompasses U.S. combat-ready fighting forces and components under the ROK/US Combined Forces Command (CFC) – a supreme command for all of the South Korean and U.S. ground, air, sea and special operations component commands. Major USFK elements include U.S. Eighth Army (EUSA), U.S. Air Forces Korea (Seventh Air Force), U.S. Naval Forces Korea (CNFK), U.S. Marine Forces Korea (MARFORK) and U.S. Special Operations Command Korea (SOCKOR).

The mission of USFK is to support the United Nations Command (UNC) and Combined Forces Command by coordinating and planning among U.S. component commands, and exercise operational control of U.S. forces as directed by United States Indo-Pacific Command. In addition, USFK is responsible for organizing, training and equipping U.S. forces on the Korean Peninsula, as well as executing ancillary functions such as non-combatant evacuation operations.

Scott Air Force Base (IATA: BLV, ICAO: KBLV, FAA LID: BLV) is a United States Air Force base in St. Clair County, Illinois, near Belleville and O'Fallon, 17 miles (27 km) east-southeast of downtown St. Louis. Originally Scott Field, it was one of 32 Air Service training camps established after the United States entered World War I in April 1917. The present base serves as the headquarters of Air Mobility Command (AMC) and its showcase wing, and it is also the headquarters of the U.S. Transportation Command, a Unified Combatant Command that coordinates transportation across all the services.

The base is operated by the 375th Air Mobility Wing (375 AMW) and is also home to the Air Force Reserve Command's 932d Airlift Wing (932 AW) and the Illinois Air National Guard's 126th Air Refueling Wing (126 ARW), the latter two units being operationally under AMC.