The world has entered the third nuclear age, and nuclear weapons are increasingly seen as valuable—and even usable—weapons by a growing number of states. Russia’s threats to use nuclear weapons, China’s rapid nuclear buildup, the United States’s unprecedentedly expensive nuclear modernization, and ongoing nuclear work in North Korea, India, Pakistan, and Iran all make clear the 21st century will be defined by nuclear risks.The re-election of President Trump is likely to accelerate many of these trends as US allies increasingly question whether the United States will defend their security in a crisis, all while it doubles down on its nuclear...