At left, the gear and garb of a Special Operations Forces soldier outfitted for serious cold. At right, a similar consumer ensemble. The difference—well, fortunately, it ain’t what it used to be. “Cotton kills” has been a truism of the outdoor world for decades, but the military is only now switching to synthetic base layers. The new gear—most of it belonging to the Personal Environmental Protective Survival Equipment (PEPSE) system—consists of ruggedized consumer tech.