The Mackinaw coat is a historic winter coat that was adopted by the U.S. Army during World War I. The early Mackinaw coat was originally made of heavy cotton duck fabric, but because the fabric was too stiff and hard to move in it was later replaced with a more comfortable cotton poplin fabric. Other improvements were also made in appearance. The shawl collar and the waist belt, which are the features of M-1942 model, were changed to the notched lapel collar while the belt was removed. By the end of the war, the name was changed from “Mackinaw coat” to ” Jeep coat”.