https://crsreports.congress.gov
Updated December 21, 2021
Defense Primer: Reserve Forces
The term reserve component (RC) refers collectively to the
seven individual reserve components of the Armed Forces.
Congress exercises authority over the reserve components
under its constitutional authority “to raise and support
Armies,” “to provide and maintain a Navy,” and “to
provide for organizing, arming, and disciplining the
Militia.... ” (Article I, Section 8)
There are seven reserve components:
Army National Guard
Army Reserve
Navy Reserve
Marine Corps Reserve
Air National Guard
Air Force Reserve
Coast Guard Reserve
The purpose of these seven reserve components, as codified
in law, 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 more units and persons are needed than are
in the regular components.” (10 U.S.C. 10102) The Army
National Guard and the Air National Guard also have an
important role under state authority, responding to various
emergencies such as disasters and civil disorders.
Difference between Federal Reserves
and National Guard
The Army Reserve, Navy Reserve, Marine Corps Reserve,
Air Force Reserve, and Coast Guard Reserve are
exclusively federal organizations. There are 54 separate
National Guard organizations: one for each state, and one
each for Puerto Rico, Guam, the U.S. Virgin Islands, and
the District of Columbia. While the District of Columbia
National Guard is an exclusively federal organization and
operates under federal control at all times, the other 53
National Guards operate as state or territorial organizations
most of the time. In this capacity, each of these
organizations is identified by its state or territorial name
(e.g., the California National Guard or the Puerto Rico
National Guard) and is controlled by its respective
governor. National Guard units and personnel can be
ordered into federal service. When this happens, control
passes from the governor of the affected units and
personnel to the President of the United States.
Reserve Categories
All reservists, whether they are in the Reserves or the
National Guard, are assigned to one of three major reserve
categories: the Ready Reserve, the Standby Reserve, or the
Retired Reserve.
Ready Reserve
The Ready Reserve is the primary manpower pool of the
reserve components. Members of the Ready Reserve will
usually be called to active duty before members of the
Standby Reserve or the Retired Reserve. The Ready
Reserve is made up of three subcomponents:
The Selected Reserve contains those units and
individuals within the Ready Reserve designated as “so
essential to initial wartime missions that they have
priority over all other Reserves.” (DOD Instruction
1215.06.) Members of the Selected Reserve are
generally required to perform one weekend of training
each month and two weeks of training each year,
although some may train more than this. When
reservists are activated, they most frequently come from
this category.
The Individual Ready Reserve (IRR) is a manpower
pool of individuals who have already received military
training, either in the Active Component or in the
Selected Reserve. They are not normally required to
perform training, but can be ordered to active duty under
certain circumstances.
The Inactive National Guard (ING) is made up of
those members of the Army National Guard who are in
an inactive status (currently there is no ING for the Air
National Guard). The ING is, for practical purposes, the
National Guard equivalent of the IRR.
There are more than one million members of the Ready
Reserve. This figure is broken down by service and
subcategory in Table 1.
Standby Reserve
The Standby Reserve contains those individuals who have a
temporary disability or hardship and those who hold key
defense-related positions in their civilian jobs. They are not
required to participate in military training and may only be
ordered to active duty in limited circumstances. There are
about 5,400 members of the Standby Reserve.
