Under arms describes a state of military readiness used to describe regular combat-ready military forces.[1] Military personnel can be generally categorized into two groups: regular forces, or the regular army, and auxiliary forces, or the reserve army. Regular forces are fully trained and fully armed, and are kept in a constant state of readiness for deployment. Auxiliary forces are given sufficient training and are only called up for service during emergencies or during large mobilizations. National Guard and military reserve forces would be classified as auxiliary forces because the majority of those personnel are usually employed full time in the civilian workforce. The Regular forces are typically not employed in any capacity other than military service, and usually reside on military bases. Therefore, the regulars are considered "under arms" while the auxiliary forces are not. A mobilization consists of the transformation of auxiliary forces into regular forces by physically amassing and arming those personnel.