Uniform of the Union Army letters US. Officers, NCOs and cavalry troopers were equipped with a sword belt with a rectangular buckle with eagle motif. Rank was displayed on epaulettes (dress occasions) or shoulder straps(field duties): no insignia for a second lieutenant, one gold bar for a first lieutenant, two gold bars for a captain, a gold oak leaf for a major, a silver oak leaf for a lieutenant colonel, a silver eagle for a colonel and one, two or three silver stars for a general, depending on his seniority. The color of the shoulder strap fields – with trims in gold braid – were
United States Army officer rank insignia or shoulder strap identified him as a commissioned officer. For majors, the shoulder strap contained an oak leaf, but like the second lieutenant, the epaulette had no grade insignia. However, the major was still distinguishable from the second lieutenant due to the more elaborate epaulette fringes worn by field grade officers. In 1872, epaulettes were abolished for officers and replaced by shoulder knots. As the shoulder knots had no fringe, it was necessary that some change in the insignia on the dress uniform be made in order to distinguish the major from the second lieutenant. It was natural to use