Bulletproof Vests A bulletproof vest is a protective covering worn to protect the torso against bullets. Body armor fell into disguise in the sixteenth and seventeenth centuries, partly because it was ineffective against bullets. Modern body armor reappeared during World War I as a means of protecting the torso from shell fragments, but the armor was too heavy to justify the protection. World War II stimulated the development of lighter body armor that consisted of overlapping plates of steel, aluminum, or bonded fiberglass attached within a nylon garment that covered both the front and back of the wearer. These "flak jackets" w