Men of the Heavy Mortar Company, 7th Infantry Regiment, cooking rice in their foxhole in the Kagae-dong area, Korea, 7 December 1950. The pile cap on the soldier at center appears to be the World War II style based on the thick visor.
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The most popular postwar winter uniform improvement was the pile cap, sometimes called the "Daniel Boone cap" by soldiers, part of the M-1951 ensemble of uniform components. It was so commonly worn during the Korean winters that it became synonymous with the Korean War.
Three versions of this cap were used in Korea. The first design was the Cap, Field, Pile, OD, a replacement for fur and knit caps that was designed in 1943 and introduced late in World War II. It was still in inventory for the Korean War. However, the World War II pattern cap was found to be impractical and was redesigned by removing the pile from the visor where it interfered with the wearer’s vision and was uncomfortable. The Model Quartermaster-1 (called "Cap, Field, Pile, OD, M-Q 1" on the label and sometimes called the M1950), adopted in January 1948, was an interim design change from the 1943 pattern that eliminated the pile on the visor.
The improved cap was eventually standardized in January 1951 as the third style, the "Cap, Field, Pile, M-1951".
An American officer in M-1951 hat waits at the UN peace negotiations in Korea.
Constructed of olive drab Shade #7 cotton poplin with a wool alpaca lining, the M1951 Pile Cap was both warm and comfortable. The ear flaps could easily be pulled down over the back and sides of the head for extra protection from cold or tied up over the crown of the cap when not needed. The front visor also could be folded down to provide glare protection, but was more often than not worn up with the wearer’s rank insignia pinned through it (officers) or stenciled on (non-coms).
The M1951 Pile Cap was widely issued, along with remaining stocks of the World War II pattern or the M-Q 1, to both U.S and allied forces serving in Korea. It proved to be a very successful design and was extremely popular for the cold Korean weather. It was one of the few items of good winter clothing that was widely available during the first harsh Korean winter of 1950-51.
The hat was soft enough that it could be worn underneath the M1 Steel Helmet as a winter liner. However, many U.S. soldiers fighting in Korea preferred to wear the lighter weight Pile Cap instead of their helmets. Since the Pile Cap obviously afforded no ballistic protection, this practice was discouraged. Nonetheless, throughout the war soldiers commonly wore the cap without the helmet. The popularity of the Pile Cap superseded, in the minds of the G.I.s, the need for protection that the much heavier helmet provided.
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