Serious reliability problems in systems subject to sudden criticality can be caused by boredom, drinking or drug taking, habit and routine, isolation, and sustained high levels of stress. Nuclear military forces require that groups of people act together, but transferring capability and responsibility from individuals to groups does not by itself protect against the limits of safety imposed by human error, illness, or malevolence. While practical steps can minimize the risks of human fallibility, there is no way to completely eliminate the potential for catastrophe in nuclear military systems except by completely eliminating nuclear weapons.