One legend tells of how when the 15th Infantry Regiment, was stationed in mainland China, the most important soldier, the one with the most stripes, in the unit had his uniform cleaned and pressed first, hence the term "first shirt".
One legend tells of how when the 15th Infantry Regiment was stationed in China, the unit landry was taken to local cleaners. The soldier with the most stripes on his shirt, (the first sergeant), had his uniform cleaned and pressed first, hence the term "first shirt".