Army patrol cap, also known as a field cap is a soft cap with a stiff, rounded visor, and flat top, worn by military personnel in the field when a combat helmet is not required.
The M1951 Army Patrol Cap, introduced with the M1951 Uniform, was a derivative of the M1943 Field Cap, part of the M1943 Uniform. The M1951 cap was worn in the Korean War, where it became known as the "patrol cap" by the US Army Rangers there.
It was constructed of wind-resistant olive drab cotton poplin, and had a flannel wool panel that folded down to cover the ears and the back of the head. It was soft enough to be worn underneath an M-1 helmet.
After the Korean War, the cap was replaced by the Ridgeway Cap, a stiffened version of the M1951. The hat became famous outside America by being worn by Fidel Castro. The patrol cap was replaced altogether, early in the Vietnam War, with a baseball-like "Cap, Field (Hot Weather)" and the boonie hat.
On June 14, 2011, the ACU became the primary headgear for all Soldiers as the duty uniform headgear - according to Army Directive 2011-11.
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