Original sentence: A small number of Reservists are selected to serve on limited tours of active duty, usually at headquarters staff level or in other special assignments.A smaller but equally important category of Reservist is the Individual Mobilization Augmentee (IMA).IMAs are Reservists who are assigned to active-duty units to do jobs that are essential in wartime but do not require full-time manning during times of peace.Most Reservists serve in the Unit Program, in which they are obligated to report for duty at least one weekend a month and an additional two weeks a year.Most Standby Reservists do not train and are not assigned to units.Reservists are categorized by several criteria in the Ready Reserve, Standby Reserve, Inactive Ready Reserve or Retired Reserve:.The Ready Reserve is made up of approximately 74,000 trained Reservists who may be recalled to active duty to augment active forces in time of war or national emergency.The Retired Reserve is made up of officers and enlisted personnel who receive pay after retiring from active duty or from the Reserve, or are Reservists awaiting retirement pay at age 60.The Standby Reserve includes Reservists whose civilian jobs are considered key to national defense or who have temporary disability or personal hardship.Their job is to bring Reserve expertise to the planning and decision-making processes at senior levels within the Air Force and other services.There are several categories of service in the Air Force Reserve.These Reservists are combat ready and can deploy to anywhere in the world in 72 hours.These Reservists no longer train, but are qualified in their fields and eligible to be recalled in the event of a national emergency.They report for duty a minimum of one day a month and 12 additional days a year