Cap, Wool, Knit, M1941"Beanie cap"

The "jeep cap" was first issued by the United States Army in February 1942 during World War II;  the purpose of the jeep cap was to be worn underneath the heavy combat helmets to offer soldiers both extra padding, and warmth. The jeep cap was originally knitted close to the head, with a six-stitch "starfish pattern" on top (supposedly to support the webbing suspension inside the helmets), with a cuff coming out like a V from the top center of the brim, and around the rest of the cap, which soldiers could pull down over their ears for even more warmth. The cap was issued in four different sizes – small, medium, large, and extra large – and made of olive drab (O.D. #3) wool

Although made specifically for wear under the steel pot helmet, the cap alone grew to be very popular with soldiers for its casual and relaxed look, and was often worn on its own. The cap was usually only issued to enlisted men, however, officers (General Patton in particular) despised the cap for its "slovenly" and "un-military" look, and it was eventually phased out and replaced with the standardized field cap, as part of the newer, layered U.S. Army M-1943 Uniform.

Authentic government issued

The jeep cap has been continued to be manufactured by the U.S. Army, however, many significant changes have been made to the cap since the original issue. For one thing, the cap is now knitted very loose and deep so it can be pulled down even lower over a soldier's head and ears for more warmth (the cuff doesn't necessarily have to be pulled down to achieve this), and instead of the old six-stitch "starfish pattern" on top, it now features a simple, more modern four-stitch topping. The cuff is now knitted completely around the entire cap, rather than coming out like a V at the center of the brim; also gone are the days of the cap being issued in four different sizes, as modern yarns are elastic enough that they are "one-size-fits-all".