Unsourced material may be challenged and removed. World War II differs from the current system. This scheme of rank insignia was established by War Department Circular No. army rank chart pdf on 5 August 1920 and would see two significant changes in 1942.
The usage of this style of insignia was ended by Department of the Army Circular No. 202, dated 7 July 1948, which provided for significant changes in both rank and insignia. Insignia of the Army of the United States”, Office of War Information. The rank of Private Specialist, usually just called a Specialist, had the command responsibilities and official insignia of a Private First Class, but also conveyed higher pay depending on the specialty and skill.
To indicate their specialty, a trade badge was sometimes inset between the chevron and the first rocker. These were often identical to the abandoned trade badges used before the reforms of 1920. Technical sergeant was renamed Sergeant First Class in 1948. A technical sergeant was often designated a platoon sergeant, acting as second-in-command.