A great number of Civil War soldiers were disabled by weapons, disease, and accidents. Initially, the permanently disabled received medical discharges from the army, but later they remained in the service and performed noncombat duties, relieving other soldiers to fight.
In 1862 the Union army allowed chief medical officers to employ "convalescent wounded and feeble men" as nurses, cooks, and hospital attendants and subsequently to organize them into detachments. Unfortunately, these methods were inefficient, and many convalescents did not return to their combat units when well.
Therefore, in Apr. 1863 the U.S. War Department created an Invalid Corps of worthy disabled officers and men who were or had been in the army. Ridicule influenced the corps to exchange its sky blue uniform for one similar to those worn by the other soldiers. The corps formed 2 "battalions," the first for those who could bear arms and perform garrison duty and the second for the severely handicapped fit only for hospital service. Late in the war the surgeon general took command of the second battalion. Like the combat units, the Invalid Corps organized officers and men into companies and regiments.
Renamed the "Veteran Reserve Corps" 18 Mar.1864, it was abolished during summer 1866. Between 1863 and 1866 more than 60,000 individuals served in the organization and performed valuable services, including garrisoning fortifications and quelling an 1863 "Draft Riot" in New York City.
The Confederacy established an Invalid Corps in 1864, in which officers and men disabled in the line of duty had to serve if they wished to receive pay. Also, if their physical condition improved sufficiently, they had to return to their combat unit. Unlike its Union counterpart, the Confederate Invalid Corps never organized companies and regiments, but a high percentage of its officers and men did perform worthwhile duties based on their disabilities and army requirements.
(Source: Historical Times Illustrated Encyclopedia of the Civil War)
http://www.civilwarhome.com/invalidcorps.htm
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