The U.S. and its allies are trying to decide whether Putin’s nuclear threats are largely bluff and whether our warnings are taken seriously…The number of annual fatalities from war has dropped precipitously since the end of World War II, despite the number of actual conflicts having increased significantly. That unprecedented development has been correctly linked to the formidable deterrent power of the nuclear forces of the United States and its allies France and the United Kingdom, a deterrent that may now be diminishing just when the U.S. has achieved a political consensus to begin a new round of necessary nuclear modernization.