What factors would propel a conventional war into a nuclear one? Would leaders know whether their military operations were driving the other toward a decision to use nuclear weapons? If we can identify potential escalation flashpoints in peacetime, what unilateral or cooperative steps can the United States and other countries take to minimize the risks of nuclear catastrophe? These are tough questions of increasing salience as competition between the United States and Russia and China intensifies. We cannot meaningfully reduce nuclear risks among the major powers if we do not understand them. Fortunately, a number of scholars and practitioners are tackling this set of issues.