Reserve components of the United States Armed Forces

The reserve components of the United States Armed Forces are military organizations whose members generally perform a minimum of 39 days of military duty per year and who augment the active duty (or full-time) military when necessary. The reserve components are also referred to collectively as the Guard and Reserves.

According to, the purpose of each reserve component is to provide trained units and qualified persons available for active duty in the armed forces, in time of war or national emergency, and at such other times as the national security may require, to fill the needs of the armed forces whenever, during and after the period needed to procure and train additional units and qualified persons to achieve the planned mobilization, more units and persons are needed than are in the regular components.

Reserve components
The eight reserve components of the U.S. military are:
 * 1) Army Reserve
 * 2) Navy Reserve
 * 3) Marine Corps Reserve
 * 4) Air Force Reserve
 * 5) Coast Guard Reserve
 * 6) Army National Guard of the United States
 * 7) Air National Guard of the United States
 * 8) United States Public Health Service Reserve Corps (*uniformed service, not an armed service)

Note: The Army National Guard of the United States and the Air National Guard of the United States primarily fall under the National Guard of the United States.

Civilian auxiliaries distinguished
The civilian auxiliaries of the U.S. military are not considered to be reserve components of the respective services but could assist the military in peacetime or wartime; the exception is the Coast Guard where upon determination by the Commandant Auxiliary members become part of the temporary Reserve (per the CG Authorization Act of 1996):


 * 1) Civil Air Patrol, auxiliary to the Air Force
 * 2) Coast Guard Auxiliary, auxiliary to the Coast Guard
 * 3) Merchant Marine, auxiliary to the Navy
 * 4) Military Auxiliary Radio System

During times of war, the Merchant Marine is classified as part of the uniformed services and members obtain veteran status.

State military forces distinguished
Additionally, the state organized militia such as various naval militias and state guards (a.k.a. state defense force) are not considered reserve components because they are not federally recognized even though they may perform a military function. However, members of the National Guard, which is a state's primary militia force, can be mobilized to support federal requirements becoming part of the National Guard of the United States.

General information
The reserve components are the embodiment of the American tradition of the citizen-soldier dating back to before the American Revolutionary War. They are regionally based and recruited (unlike their active duty counterparts) and, in the case of the Army and Air National Guard, are the organized state militias referred to in the U.S. Constitution. Members of the reserve components are generally required to perform, at a minimum, 39 days of military service per year. This includes monthly drill weekends and fifteen days of annual training (giving rise to the old slogan “one weekend a month, two weeks a year”).

While organized, trained, and equipped nearly the same as the active duty, the reserve components often have unique characteristics. This is especially true of the National Guard, which performs both federal and state missions. In addition, reserve components often operate under special laws, regulations, and policies.

Reserve vs. National Guard
The Reserve Components of the United States Armed forces are named within Title 10 of the United States Code and include: (1) the Army National Guard of the United States, (2) the Army Reserve, (3) the Navy Reserve, (4) the Marine Corps Reserve, (5) the Air National Guard of the United States, (6) the Air Force Reserve, and (7) the Coast Guard Reserve. In practice the use of the term “reserve” varies depending on the context in which it is used. In one context, as used here in this article, it applies to all seven of the reserve components of the U.S. military. In another context, it applies to only the five reserve components directly associated with the five active duty military services but neither to the Army National Guard nor the Air National Guard.

In most respects, the Army National Guard and Air National Guard are very similar to the Army Reserve and Air Force Reserve, respectively. The primary difference lies in the level of government to which they are subordinated. The Army Reserve and Air Force Reserve are subordinated to the federal government while the National Guards are subordinated to the various state governments, except when called into federal service by the President of the United States or as provided for by law. For example, the California Army National Guard and California Air National Guard are subordinated to the state of California and report to the governor of California as their commander-in-chief.

This unique relationship descends from the colonial and state militias that served as a balance against a standing federal army, which many Americans feared would threaten states’ rights. The militias were organized into the present National Guard system with the Militia Act of 1903.

Besides the theoretical check on federal power, the distinction between the federal military reserves and the National Guard permits state governors to use their personnel to assist in disaster relief and to preserve law and order in times of crisis. The latter is permitted because the National Guard are not subject to the restrictions of the Posse Comitatus Act unless they are under federal jurisdiction. The restrictions, however, do apply to the four of the other five reserve components just as it does with their active duty military counterparts. The United States Coast Guard and United States Coast Guard Reserve are not subject to the restrictions of the Posse Comitatus Act because they are the only Armed Force of the United States that is not part of the United States Department of Defense.

National Guard vs. National Guard of the United States
While the National Guard is a militia force organized by each state, the National Guard of the United States is a reserve federal military force of the United States Armed Forces. The National Guard of the United States is joint reserve component of the United States Army and the United States Air Force and are made up of National Guard members from the states appointed to federal military service under the consent of their respective state governors. The National Guard of the United States maintains two subcomponents: the Army National Guard of the United States for the Army and the Air Force's Air National Guard of the United States. The Army National Guard of the United States is made up of federally recognized members of the Army National Guard and the Air National Guard of the United States is made up of federally recognized members of the Air National Guard.

Reserve component categories
All members of a reserve component are assigned to one of three reserve component categories:
 * The Ready Reserve comprises military members of the Reserve and National Guard, organized in units or as individuals, liable for recall to active duty to augment the active components in time of war or national emergency. The Ready Reserve consists of three reserve component subcategories:
 * The Selected Reserve consist of those units and individuals within the Ready Reserve designated by their respective Services and approved by the Chairman of the Joint Chiefs of Staff as so essential to initial wartime missions that they have priority over all other Reserves. The Selected Reserve consists of additional sub-subcategories:
 * Drilling Reservists/Troop Program Units (TPUs) are trained unit members who participate in unit training activities on a part-time basis.
 * Training Pipeline (non-deployable account) personnel are enlisted members of the Selected Reserve who have not yet completed initial active duty for training (IADT) and officers who are in training for professional categories or in undergraduate flying training.
 * Individual Mobilization Augmentees (IMAs) are trained individuals assigned to an active component, Selective Service System, or Federal Emergency Management Agency (FEMA) organization’s billet which must be filled on or shortly after mobilization. IMAs participate in training activities on a part-time basis with an active component unit in preparation for recall in a mobilization.
 * Active Guard/Reserve (AGR) are National Guard or Reserve members of the Selected Reserve who are ordered to active duty or full-time National Guard duty for the purpose of organizing, administering, recruiting, instructing, or training the reserve component units.
 * Individual Ready Reserve (IRR) personnel provide a manpower pool composed principally of individuals having had training, having previously served in an active duty component or in the Selected Reserve, and having some period of their military service obligation (MSO) remaining.
 * Inactive National Guard (ING) are National Guard personnel in an inactive status in the Ready Reserve, not in the Selected Reserve, attached to a specific National Guard unit, who are required to muster once a year with their assigned unit but do not participate in training activities. On mobilization, ING members mobilize with their units.
 * The Standby Reserve consists of personnel who maintain their affiliation without being in the Ready Reserve, who have been designated key civilian employees, or who have a temporary hardship or disability. They are not required to perform training and are not part of units but create a pool of trained individuals who could be mobilized if necessary as a last resort to fill manpower needs in specific skills. Membership in the Standby Reserve is limited to one year, afterwards the Soldier must determine if they are transferring to the IRR or a drilling unit.
 * Active Status List are those Standby Reservists temporarily assigned for hardship or other cogent reason; those not having fulfilled their military service obligation or those retained in active status when provided for by law; or those members of Congress and others identified by their employers as “key personnel” and who have been removed from the Ready Reserve because they are critical to the national security in their civilian employment.
 * Inactive Status List are those Standby Reservists who are not required by law or regulation to remain in an active program and who retain their Reserve affiliation in a non-participating status, and those who have skills which may be of possible future use to the Armed Force concerned.
 * The Retired Reserve consists of all Reserve officers and enlisted personnel who receive retired pay on the basis of active duty and/or reserve service; all Reserve officers and enlisted personnel who are otherwise eligible for retired pay but have not reached age 60, who have not elected discharge, and are not voluntary members of the Ready or Standby Reserve; and other retired reservists under certain conditions.

Mobilization
Individual service members or entire units of the reserve components may be called into active duty (also referred to as mobilized, activated, or called up), under several conditions:


 * Full Mobilization requires a declaration of war or national emergency by the United States Congress, affects all reservists (including those on inactive status and retired members), and may last until six months after the war or emergency for which it was declared.
 * Partial Mobilization requires a declaration of national emergency, affects only the Ready Reserve, and is limited to a maximum of one million personnel activated for no more than two years.
 * Presidential Reserve Call-Ups do not require a declaration of national emergency but require the President to notify Congress and is limited to 200,000 Selected Reservists and 30,000 Individual Ready Reservists for up to 270 days.
 * The 15-Day Statute allows individual service secretaries to call up the Ready Reserves for up to 15 days per year for annual training or operational missions.
 * RC Volunteers may request to go on active duty regardless of their reserve component category, but state governors must approve activating National Guard personnel.