AR 140-1 governs policy guidance on the mission, organization, and training of the U.S. Army Reserve.
View AR 140-1 on armypubs.army.mil
It covers USAR composition, command channels, troop program units, training programs, aviation, marksmanship, training institutions, and ambassador activities. It requires units supporting contingency operations or mobilization to have prescribed strength, proper training, and enough equipment.
The USAR is a statutory Federal force which consists of the Ready Reserve, the Standby Reserve, and the Retired Reserve. (paragraph 1-7)
The USAR mission is to meet DA contingency operations or mobilization requirements. (paragraph 1-8)
USAR RTUs are organized to train nonunit USAR soldiers. (paragraph 2-7)
At least 10 soldiers are required to form an RTU. (paragraph 2-7)
The longest distance a soldier can be expected to travel involuntarily between his or her residence and a site where inactive duty training (IDT) will be conducted. (paragraph 6-73)