In one of its collections, the Art Institute of Chicago displays rows of medieval European weaponry—swords, rapiers, maces, daggers, helmets, shields and suits of armor—all encased in glass, every detail lit up by museum lights. The tools of war are both frightening and beautiful, with their intricate etchings and gilded filigrees distracting the viewer from their brutal purpose. On my first visit I was struck by the neat correlation between tools designed for killing and tools designed to thwart killing blows. There is a helmet for every mace, a breastplate for every dagger and a shield for every sword. The pairing suggests defense and aggression sitting side by side in an arrested state. In bizarre neutrality, humanity’s murderous intent is checked, blocked and stopped by the quality of its armor.