Noah Millman walks us through various nuclear arms chess matches:
The main reasons to pursue strategic arms reductions with Russia are: the arms are actually worthless, so eliminating them saves both us and the Russians money, and increases global well-being directly thereby; and the reductions may help us get better support from allies like France and Germany in pursuing stricter controls on nuclear technology transfer (which is one practical way to combat proliferation). The real successes in nuclear-counter-proliferation, however, all fall into three categories: allies who have not needed to go nuclear because they are under the American nuclear umbrella (Germany, Japan, South Korea); neutrals or allies who no longer have significant in-region enemies or rivals against whom they might want to wield a nuclear deterrent (South Africa, Brazil, Argentina); and countries that gave up or have not built nuclear weapons for fear of provoking a much stronger neighbor (Taiwan, Kazakhstan, Ukraine). So the real investment in counter-proliferation is investment in conflict-reduction. Unfortunately, South Asia is the least-likely territory for conflict reduction, just as it is the least likely to be directly responsive to US-Russian moves, while simultaneously it is the most likely venue for war actually escalating to the nuclear level.