Can the law of armed conflict—a sometimes nebulous body of international law developed incrementally over centuries through both custom and treaty—keep up with the unprecedented pace of development in military technology and weaponry? Reports that may seem like science fiction detailing technological breakthroughs are all around us. Global powers are infiltrating the civilian electrical power grids and other critical infrastructure of potential adversaries, perhaps in part to prepare opportunities to deploy cyber weapons in a future armed conflict. Artificial intelligence algorithms designed to engage in air warfare have begun competing with, and perhaps one day will surpass, human military pilots. Weapons that have existed for decades are rapidly developing more effective capabilities, for example, missiles that travel far faster than sound and thus perhaps require defense systems that detect and respond more quickly than humans.