Campaign Hats have been authorized for wear only by Drill Sergeants since the mid-1960s, but from their introduction in 1872 though the end of World War II they were worn by Soldiers, NCOs, Officers, Warrant Officers, and even Generals. As was so often the case with uniforms in the late 19th century, Enlisted troops and Officers alike often took liberties adorning their garments with insignia, sometimes spurring the Army to adopt some of their more common-sense modifications.
One of their sartorial inventions was looping hat cords worn around the bottom of the crown of the Campaign Hat and other types of headgear, and around 1890 the War Department began specifying the colors of the hat cords. In 1899, the War Department specified that the hat cords for Fatigue Hats worn by Enlisted personnel were to be in the “color of arm of service” which had been delineated in uniform regulations published earlier that year.
The first reference to black-and-gold hat cords for Commissioned Officers had come in January of that year in a General Order mandating a gold cord for General Officers and a cord of “black and silk intermixed” for all other Officers. (The combination of silver and black was established for Warrant Officers, or Army Field Clerks to be more precise, in December 1917.) The mixture of black-and-gold cord and gold acorns was first announced in 1921 in AR 600-35, which stated that hat cords for “other Officers” were to be “a cord…of gold bullion and black silk intermixed, the acorns and keeper to be of gold bullion.”
Although Campaign Hats were discontinued after World War II, highly similar “Campaign Stetson” or “Cav Hats” became popular among Air Cavalry units in Vietnam, and before that some marksmanship teams used them because of their functionality on a rifle range. They were officially brought back only for Drill Sergeants at some point in the mid-1960s.