Just prior to World War II , ponchos were significantly improved during testing with the . Army Jungle Experimental Platoon in the jungles of Panama , incorporating new, lighter materials and a drawcord hood that could be closed off to form a rain fly or ground sheet.  Ponchos were widely used by United States armed forces during World War II; even lightly equipped foot-mounted forces such as Merrill's Marauders , forced to discard tentage and all other unnecessary equipment, retained their blanket and poncho.  During the 1950s, new lightweight coated nylon and other synthetic materials were developed for military ponchos. The poncho has remained in service ever since as a standard piece of . military field equipment.  Today, the United States armed forces issue ponchos that may be used as a field expedient shelter. These garments are also used by hunters , campers , and rescue workers.