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Updated December 21, 2021
Defense Primer: Reserve Forces
The term reserve component (RC) refers collectively to the
passes from the governor of the affected units and
seven individual reserve components of the Armed Forces.
personnel to the President of the United States.
Congress exercises authority over the reserve components
under its constitutional authority “to raise and support
Reserve Categories
Armies,” “to provide and maintain a Navy,” and “to
All reservists, whether they are in the Reserves or the
provide for organizing, arming, and disciplining the
National Guard, are assigned to one of three major reserve
Militia.... ” (Article I, Section 8)
categories: the Ready Reserve, the Standby Reserve, or the
Retired Reserve.
There are seven reserve components:
Ready Reserve
Army National Guard
The Ready Reserve is the primary manpower pool of the
reserve components. Members of the Ready Reserve will
Army Reserve
usually be called to active duty before members of the
Standby Reserve or the Retired Reserve. The Ready
Navy Reserve
Reserve is made up of three subcomponents:
Marine Corps Reserve
The Selected Reserve contains those units and
individuals within the Ready Reserve designated as “so
Air National Guard
essential to initial wartime missions that they have
priority over all other Reserves.” (DOD Instruction
Air Force Reserve
1215.06.) Members of the Selected Reserve are
generally required to perform one weekend of training
Coast Guard Reserve
each month and two weeks of training each year,
although some may train more than this. When
The purpose of these seven reserve components, as codified
reservists are activated, they most frequently come from
in law, is to “provide trained units and qualified persons
this category.
available for active duty in the armed forces, in time of war
or national emergency, and at such other times as the
The Individual Ready Reserve (IRR) is a manpower
national security may require, to fill the needs of the armed
pool of individuals who have already received military
forces whenever more units and persons are needed than are
training, either in the Active Component or in the
in the regular components.” (10 U.S.C. 10102) The Army
Selected Reserve. They are not normally required to
National Guard and the Air National Guard also have an
perform training, but can be ordered to active duty under
important role under state authority, responding to various
certain circumstances.
emergencies such as disasters and civil disorders.
The Inactive National Guard (ING) is made up of
Difference between Federal Reserves
those members of the Army National Guard who are in
and National Guard
an inactive status (currently there is no ING for the Air
The Army Reserve, Navy Reserve, Marine Corps Reserve,
National Guard). The ING is, for practical purposes, the
Air Force Reserve, and Coast Guard Reserve are
National Guard equivalent of the IRR.
exclusively federal organizations. There are 54 separate
National Guard organizations: one for each state, and one
There are more than one million members of the Ready
each for Puerto Rico, Guam, the U.S. Virgin Islands, and
Reserve. This figure is broken down by service and
the District of Columbia. While the District of Columbia
subcategory in Table 1.
National Guard is an exclusively federal organization and
operates under federal control at all times, the other 53
Standby Reserve
National Guards operate as state or territorial organizations
The Standby Reserve contains those individuals who have a
most of the time. In this capacity, each of these
temporary disability or hardship and those who hold key
organizations is identified by its state or territorial name
defense-related positions in their civilian jobs. They are not
(e.g., the California National Guard or the Puerto Rico
required to participate in military training and may only be
National Guard) and is controlled by its respective
ordered to active duty in limited circumstances. There are
governor. National Guard units and personnel can be
about 5,400 members of the Standby Reserve.
ordered into federal service. When this happens, control
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Defense Primer: Reserve Forces
Table 1. Ready Reserve Personnel Strength
As of September 30, 2021
Individual Ready Reserve &
Ready Reserve
Reserve Component
Selected Reserve
Inactive National Guard
Total
Army National Guard
337,525
809
338,334
Army Reserve
184,358
86,201
270,559
Navy Reserve
57,632
38,665
96,297
Marine Corps Reserve
35,240
63,631
98,871
Air National Guard
108,483
0
108,483
Air Force Reserve
70,570
26,330
96,900
Coast Guard Reserve
6,256
1,795
8051
Total
800,064
217,431
1,017,495
Source: Defense Manpower Data Center.
Retired Reserve
In addition to activations under federal authority, members
The Retired Reserve includes Reserve personnel who are
of the National Guard can also be activated by their
receiving retired pay or who transfer into the Retired
governor for full time duty (i.e., state active duty) owing to
Reserve after qualifying for reserve retirement, but before
their unique state/federal status. They can also be activated
becoming eligible to receive retired pay. Members of the
under state control but with pay and benefits provided by
Retired Reserve may be ordered to active duty only in
the federal government. This is sometimes referred to as
limited circumstances. There are about 788,000 members of
Title 32 status in reference to the part of the United States
the Retired Reserve.
Code that governs this duty status.
Full-Time Support
Pay, Benefits, and Duty Status
Reserve units are primarily filled by traditional reservists:
Reservists’ pay and benefits may vary significantly based
members of the Selected Reserve who are usually required
on the type of duty performed. Some key variables in
to work one weekend a month and two weeks a year.
determining the compensation provided include (1) whether
However, many reserve units are also staffed by one or
an individual is performing active duty or inactive duty; (2)
more full-time civilian and/or military employees. These
if on active duty, the statutory authority under which the
employees, known as full-time support (FTS) personnel, are
individual is activated, the duration of the duty, and
“assigned to organize; administer; instruct; recruit and train;
whether the duty performed is in support of a contingency
maintain supplies, equipment and aircraft; and perform
operation; and (3) for the National Guard, whether the duty
other functions required on a daily basis in the execution of
is in a state status or federal status.
operational missions and readiness preparations.... ”(DOD
Instruction 1205.18).
Relevant Statutes
Activations
Title 10, U.S. Code, Subtitle E (Reserve Components)
At present, there are four statutory provisions by which
Title 32, U.S. Code (National Guard)
members of the National Guard and Reserve can be
involuntarily ordered to federal active duty for a year or
more. Three of these authorities have existed for decades,
and are commonly referred to as Full Mobilization (10 USC
CRS Products
12301(a)), Partial Mobilization (10 U.S.C. 12302), and
CRS Report RL30802, Reserve Component Personnel Issues:
Presidential Reserve Call-up (10 U.S.C. 12304). The fourth
Questions and Answers, by Lawrence Kapp and Barbara Salazar
authority, added in 2011, allows reservists to be activated to
Torreon
support the Combatant Commands for preplanned missions
(10 U.S.C. 12304b). These provisions differ from each
CRS Report R43808, Army Active Component (AC)/Reserve
other in terms of the statutory requirements for utilization,
Component (RC) Force Mix: Considerations and Options for
the number and category of reservists called up, and the
Congress, by Andrew Feickert and Lawrence Kapp
duration of the call up. Another authority added in 2011
provides for involuntarily activating members of the Army
Reserve, Navy Reserve, Marine Corps Reserve, and Air
Force Reserve to respond to major disasters or emergencies,
Lawrence Kapp, Specialist in Military Personnel Policy
for periods of up to 120 days (10 U.S.C. 12304a).
IF10540
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Defense Primer: Reserve Forces
Disclaimer
This document was prepared by the Congressional Research Service (CRS). CRS serves as nonpartisan shared staff to
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