The term "Reserve Component" (RC) refers collectively to the seven individual reserve components of the Armed Forces: the Army National Guard of the United States, the Army Reserve, the Navy Reserve, the Marine Corps Reserve, the Air National Guard of the United States, the Air Force Reserve, and the 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." The Army National Guard and the Air National Guard also have a state role: operating under the control of their governor, they respond to various domestic emergencies, such as disasters and civil disorders. (For more information on the difference between the National Guard and other reserve components, see questions 5 and 11.) All individual reservists, whether members of the Reserve or the National Guard, are assigned to one of three major reserve categories: the Ready Reserve, the Standby Reserve, or the Retired Reserve. Reservists who are assigned to the Ready Reserve are further assigned to one of its three sub-components: the Selected Reserve, the Individual Ready Reserve (IRR), or the Inactive National Guard (ING). The differences between each of these categories are explained below. 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 comprises the Selected Reserve, the Individual Ready Reserve, and the Inactive National Guard, each of which is described below. 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. Members of the Selected Reserve are generally required to perform one weekend of training each month ( inactive duty for training or IDT, also known colloquially as weekend drill ) and two weeks of training each year (annual training or AT) for which they receive pay and benefits. Some members of the Selected Reserve perform considerably more military duty than this, while others may only be required to perform the two weeks of annual training each year or other combinations of time. Members of the Selected Reserve can be involuntarily ordered to active duty under each of the main activation authorities (for example, Full Mobilization, Partial Mobilization, and Presidential Reserve Call-up; see question 9 for more information on activation authorities). The Individual Ready Reserve (IRR) is a manpower pool primarily composed of individuals who have already received military training, either in the Active Component or in the Selected Reserve. By law, members of the IRR may be required to perform regular training, but the Department of Defense does not currently require this. Members of the IRR can volunteer for training or active duty assignments, and they can also be involuntarily ordered to active duty under a Full Mobilization, Partial Mobilization, or a Disaster Response Activation. There is also a category of the IRR that can be activated during a Presidential Reserve Call-up, but at present there is no one assigned to this category. (See question 9 for more information on these activation authorities.) There is no IRR in the Army National Guard or the Air National Guard, although there is an analogous category in the Army National Guard known as the Inactive National Guard (see " The Inactive National Guard ," immediately below). The Inactive National Guard (ING) is, for practical purposes, the National Guard equivalent of the IRR. It comprises those members of the Army National Guard who are in an inactive status; currently there is no ING for the Air National Guard. They do not participate in training as do members of the Selected Reserve; however, they are attached to a specific National Guard unit and are required to meet with the unit once a year. Members of the ING can be involuntarily ordered to active duty if the unit they are attached to is activated under a Partial Mobilization, or a Full Mobilization. They are not subject to activation under a Presidential Reserve Call-up. (See question 9 for more information on these activation authorities.) The Standby Reserve comprises those individuals who have a temporary disability or hardship and those who hold key defense related positions in their civilian jobs. While in the Standby Reserve, reservists are not required to participate in military training and are subject to involuntary activation only in the case of a full mobilization. (See question 9 for more information on these activation authorities.) The Retired Reserve includes (1) Reserve officers and enlisted personnel who are receiving retired pay as a result of their reserve and/or active service; and (2) Reserve officers and enlisted personnel who transfer into the Retired Reserve after qualifying for reserve retirement, but before becoming eligible to receive retired pay (which normally occurs at age 60). Regular officers and enlisted personnel who are receiving retired pay are not included in the Retired Reserve. Members of the Retired Reserve may be involuntarily ordered to active duty in the event of a full mobilization, and some members of the Retired Reserve may be ordered to active duty in the event of a recall of retirees. (See " 9. How Are Reservists Called to Active Duty by the Federal Government? " for more information on activation authorities.) As of July 31, 2018, the total reported personnel strength of the Ready Reserve was 1,036,644. Table 1 breaks down this figure by service and category of reservist. In addition, there are about 13,000 members of the Standby Reserve and about 780,000 members of the Retired Reserve, although these categories of reservists are much less likely to be mobilized than Ready Reservists. Additionally, a substantial percentage of the Retired Reserve would likely be unable to mobilize due to age and fitness. Although the Reserves have been used extensively in support of operations since September 11, 2001, the overall authorized end-strength of the Selected Reserve declined by about 6% between 2001 and 2018 (874,664 for FY2001 versus 823,900 for FY2018). The largest reduction in authorized end-strength occurred in the Navy Reserve (-29,900 or -33.6%), while smaller reductions occurred in the Coast Guard Reserve (-1,000 or 12.5%), Air Force Reserve (-4,558 or -6.1%), Army Reserve (-5,800 or -2.8%), Marine Corps Reserve (-1,058 or -2.7%), Army National Guard (-7,026 or -2.0%), and Air National Guard (-1,422 or -1.3%). Reserve units are primarily filled by traditional reservists: members of the Selected Reserve who are usually required to work one weekend a month and two weeks a year. However, most reserve units are also staffed by one or more full-time civilian and/or military employees. These employees, known as full-time support (FTS) personnel, are "assigned to organize; administer; instruct; recruit and train; maintain supplies, equipment and aircraft; and perform other functions required on a daily basis in the execution of operational missions and readiness preparations" as authorized in Title 10, Title 5, and Title 32. There are five types of FTS personnel: Active Guard & Reserve, Military Technician, Non-Dual Status Technician, Active Component, and Civilian. The distinctions between each of these categories are outlined below. The mix of FTS personnel in each of the reserve components (RC) is intended "to optimize consistency and stability for each RC to achieve its assigned missions." Table 2 provides a summary of FTS personnel strength, broken down by service and category. Active Guard and Reserve (AGR) personnel are members of a Reserve Component who are placed on active duty or full-time National Guard duty orders for a period of 180 consecutive days or more for the purpose of "organizing, administering, recruiting, instructing, or training the reserve components." They may also perform certain operational support duties, and certain duties related to defense against weapons of mass destruction, as well as provide training to active component personnel, DOD contractors, DOD civilians, and foreign military personnel. Although they are serving full-time, AGR personnel are still considered members of the Selected Reserve. They are usually required to attend weekend drills and annual training with the reserve unit to which they are assigned. Depending on their branch of service, AGR personnel are referred to by different names. In the Army National Guard, Army Reserve, Air National Guard, and Air Force Reserve, they are simply referred to as AGRs, an acronym for Active Guard and Reserve. In the Navy Reserve they are referred to as TARs, an acronym for Training and Administration of Reserves. In the Marine Corps Reserve, they are known as Marine Corps Active Reserves or ARs. Military technicians (MTs) – referred to in statute as "military technicians (dual status)" -- are federal civilian employees who provide support to reserve units, either in the "organizing, administering, instructing or training of the Selected Reserve" or by maintaining and repairing reserve component equipment and supplies. Some MTs may also perform certain operational support duties and provide training to active component personnel, DOD contractors, DOD civilians, and foreign military personnel. Unlike regular civilian employees, MTs are generally required to maintain membership in the Selected Reserve as a condition of their employment. They are required to attend weekend drills and annual training with their reserve unit, which is usually the one that employs them as civilians during the week. Military technicians can be involuntarily ordered to active duty in the same way as other members of the Selected Reserve (see " 2. What Are the Different Categories of Reservists? "). There are no MTs in the Navy Reserve, the Marine Corps Reserve, or the Coast Guard Reserve.