U.S. Army Regimental System

The United States Army Regimental System (USARS) is an organizational and classification system used by the United States Army. It was established in 1981 to replace the Combat Arms Regimental System (CARS) to provide each soldier with continuous identification with a single regiment, and to increase a soldier's probability of serving recurring assignments with their regiment.

Source: Wikipedia — U.S. Army Regimental System (CC BY-SA 4.0)