Through World War I, soldiers in the United States Army wore a comfortable loose-fitting wool four pocket field garment.
[1] At the end of the 1930s, the Army moved to adopt a new outer garment that was intended to be more utilitarian and provide better protection in combat.
A further reason for adopting a field jacket made of a different material was that shortages of wool were expected.
The Olive Drab Cotton Field Jacket was standardized and adopted in June 1940 for use by all members of the US Army for wear with both the winter and summer service uniforms.
The jacket was modeled after a civilian windbreaker design, and was constructed of an olive drab shade 2 cotton poplin outer shell with a dark olive drab blanket wool flannel lining, with shell color on new jackets was a pale pea-green color, but faded fairly quickly with heavy use and sun exposure to the more common beige-green.
cotton field jacket was the standard outer garment for all army personnel, except those that had other specialist clothing (Paratroopers wore the parachutist's coat and trousers, tank crews wore the tanker's jacket, various types of parkas were worn in cold weather, etc.).
Photographic evidence shows that soldiers continued to wear the older jacket all the way through the end of the war, due to supply shortages and squabbling between the Quartermaster Corps and field commanders, who all had their own ideas of what the troops should "look like".
Its main differences were that it was made with a more water resistant fabric and had buckles for tightening around the wrists and waist instead of buttons.