Sentence:  It is likely that some of the younger men who had been too young to participate in the Civil War may have seen the <WSD>Red Shirt</WSD> companies as their opportunity to share in "the glory of battle" and were happy to join their fathers and older brothers. 
Meaning of the word marked with <WSD> tags:  A member of a paramilitary arm of the Democratic party in Mississippi and South Carolina at the end of Reconstruction.