Thinking about the Unthinkable in a Highly Proliferated World

For decades, the United States has led the effort to stem the spread of nuclear weapons, both among potential adversaries and among its allies and partners. The current state of deterrence and of the nonproliferation regime, however, is open to many doubts. What happens if the nonproliferation regime should break down altogether? What happens if extended deterrence should fail, and allies no longe...