But whereas Russia's nuclear capabilities have decayed, and China's have remained largely static, America's have become far more lethal. Although the U.S. arsenal has diminished in size, it has also—reflecting the seemingly exponential progress of the U.S. military's technological revolution—grown both immensely more accurate and immensely more powerful. The Navy, for instance, has refitted its entire SSBN fleet to carry the new, highly accurate Trident II, a missile whose already stunning precision has been nearly continuously upgraded. The Navy has also deployed 400 W88 warheads, which are nearly five times as powerful as the Trident II's Cold War—era warhead. Minuteman III ICBMs have been retrofitted with much more accurate guidance systems and higher-yield warheads.
These improvements are inconsistent with the aim of simply deterring an adversary's nuclear attack—a goal that would require merely a "countervalue" strike on the enemy's cities. They are necessary for a disarming "counterforce" strike, aimed at pre-empting a nuclear attack—and hence winning a nuclear war. Similarly, the avionics upgrades to the B-2 stealth bombermake sense only if that plane is to be directed against the most technologically sophisticated peer competitor, not against a "rogue state" such as Iran or North Korea. Washington's intentions can't, of course, be definitely determined, but as a RAND report on the future roles of the U.S. nuclear arsenal concluded in 2003, "What the planned force appears best suited to provide beyond the needs of traditional deterrence is a preemptive counterforce capability against Russia and China. Otherwise, the numbers and the operating procedures simply do not add up" (emphasis in original).
In a feat of technical sophistication and strategic insight, Lieber and Press have modeled a U.S. first strike against Russia. (Although China is Washington's most probable great-power rival, the authors argue, Russia presents a "hard case" for their contention that America has achieved nuclear ascendancy.) That model, which they presented at the Council on Foreign Relations in October, has been vetted by most of the top civilian defense analysts. To be conservative, it assumes that U.S. nuclear weapons will perform with much less accuracy and reliability than should be expected. Even so, the authors conclude, a U.S. attack today would destroy the entire Russian nuclear arsenal. To grossly oversimplify: the erosion of Russian capabilities, combined with new, overwhelming warhead yields and the "accuracy revolution" in U.S. nuclear forces, has largely obviated the problems of "fratricide" (the prospect that U.S. missiles on the attack would destroy each other, leaving their targets safe) that once helped make a disarming strike impossible to achieve.
Lieber and Press emphasize that their analysis doesn't prove that a U.S. first strike would succeed, but it highlights a development that is grave if only because it's one that prudent planners in Russia and China, who conduct similar analyses, are no doubt already surmising: that their countries can no longer be confident of having a viable deterrent. Surely adding to their alarm is the realization that the nuclear imbalance, troubling enough already, will only grow in the coming years. Washington's withdrawal from the Anti-Ballistic Missile Treaty and its concomitant pursuit of a national missile-defense system will greatly enhance its offensive nuclear capabilities, because although critics of missile defense correctly argue that it could never shield America from a massive full-scale nuclear attack, it could quite plausibly deal with the very few missiles an adversary might have left to deploy after a U.S. first strike. What's more, the United States is actively pursuing a series of initiatives—including further advances in anti-submarine and anti-satellite warfare; in missile accuracy and potency; and in wide-area remote sensing, aimed at finding "relocatable" targets such as mobile ICBMs—that will render Russia's and China's nuclear forces all the more vulnerable.