One of the most important challenges facing U.S. leaders in the post-Cold War era is keeping the United States out of regional disputes in which one or more of the parties might be armed with nuclear weapons. Washington's obsession with preventing nuclear proliferation, combined with the doctrine of extended deterrence, instead puts the United States on the front lines of such conflicts. The most worrisome situations are those involving the two Koreas, Pakistan and India, and Ukraine and Russia.
Amid mounting evidence that North Korea may be pursuing a nuclear-weapons capability, the United States maintains a mutual defense treaty with South Korea and stations 36,000 troops on the peninsula. Washington's exposure in the simmering confrontation between Pakistan and India is less severe, but a 1959 military agreement contains an obligation to aid Pakistan in case of aggression. U.S. officials flirt with providing Kiev with security guarantees in the forlorn hope of inducing Ukrainian officials to relinquish the nuclear weapons stationed on their territory.
Washington's willingness to shield friendly nations from their regional adversaries does provide an incentive for its protectorates to forgo the development of independent nuclear arsenals. The threat of U.S. retaliation also might deter an aggressive nuclear power from attacking its neighbors. Such commitments, however, greatly increase the probability that the United States would be entangled in any conflict that did erupt. Instead of assuming grave risks when vital American security interests are not at stake, the United States should distance itself from regional disputes that could go nuclear.