Vests are far from foolproof. Here's What You Need To Remember: Although armor may stop shrapnel, most armor protection lacks coverage for the face, arms, legs and below the waist. The concussive force of explosions can also damage unprotected limbs, create traumatic brain injuries and cause internal injuries—even behind body armors. For decades, protection lagged far behind lethality on the battlefield. The only practical protection from bullets and dangerous flying objects was steel, but weight forced a tradeoff between protection and mobility; adequate protection could render a soldier perfectly immobile. A compromise of equipping a soldier with enough steel to stop light shrapnel, ricochets and other flying objects—but not actual bullets—held from World War I to just after the Vietnam War.