Mark with US Army Shoulder Sleeve Insignia: 1st | #400644

The United States Army is one of the three military departments (Army, Navy and Air Force) which reports to the Department of Defense. The modern US Army has its roots in the Continental Army, which was formed on 14 June 1775. I and II Field Force, Vietnam was a United States Army Corps-level command during the Vietnam War. A shoulder sleeve insignia (SSI), is an embroidered patch worn on some uniforms of the United States Army. The SSI in this image was approved for the 1st Field Force, Vietnam on 5 October 1966.