Mike Krepon has an excellent discussion of these issues in a new Foreign Affairs piece.
The current nuclear landscape is foreboding. All of the existing foundations of the global nuclear order have been weakened. Some arms-control and reduction treaties have been altogether jettisoned, while other constraints are eroding.
When U.S. President-elect Donald Trump takes office in January, he will face a global nuclear order that is increasingly unstable. North Korea, deteriorating U.S.–Russian relations, and the triangular competition among India, Pakistan, and China are all cause for concern. Add in Beijing’s growing ambitions to control resources and sea-lanes around its periphery and Trump’s repeated promises to rip up the Iran nuclear agreement, and the future of global nuclear arms control looks even more uncertain.The incoming president has, of course, made contradictory comments on nuclear issues, so he could move in reassuring directions. Let's hope he does.