F. E. WARREN AIR FORCE BASE, Wyo. -- It has been argued in some circles that U.S. nuclear warhead modernization efforts would give countries incentive to acquire or improve nuclear weapons and thus undermine nonproliferation efforts. This concern is foremost among those Americans who oppose newly designed nuclear warheads, including the former Reliable Replacement Warhead. However, a likely root cause for nuclear proliferation, and hesitation to participate in nuclear disarmament discussions, lies in the overwhelming dominance of U.S. conventional military capabilities.

The desire of actual or potential adversaries to acquire nuclear weapons is more likely driven by superior U.S. conventional military capabilities and the possibility of their use than the size and composition of the U.S. nuclear stockpile or associated military delivery capabilities. According to the Department of Defense, the U.S. nuclear stockpile has undergone an approximately 80 percent decrease in total numbers since its Cold War height. Delivery vehicles or platforms decreased significantly as well.

Meanwhile, U.S. conventional military capabilities have increased dramatically with the advent of advanced technologies, such as stealth aircraft, armed and unarmed unmanned aerial vehicles, ballistic missile defense and GPS-guided weaponry among others. Proliferation efforts of actual or potential adversaries have occurred predominantly during this period of significant decline in numbers and composition of U.S. nuclear forces -- and after game-changing demonstrations of preeminent U.S. conventional capabilities in 1991 Iraq, Kosovo, Afghanistan, and 2003 Iraq.

A different type of potential proliferation, among U.S.-friendly countries that could decide to withdraw from the Nuclear Nonproliferation Treaty and develop their own nuclear warheads, is significantly influenced by the size of U.S. nuclear stockpile and not by conventional military capabilities. These countries may feel forced to pursue this alternative, in their national interest, if the U.S. stockpile decreases -- without reciprocal Russian and Chinese stockpile cuts -- to a point where they no longer believe the U.S. can meet its extended deterrence commitments. This possibility should not preclude efforts to decrease worldwide nuclear warhead stockpiles to responsible levels, but should serve as a reminder that many factors must be considered before making unilateral or bilateral reductions in the nuclear stockpile.

Regarding vertical proliferation, U.S. conventional military capabilities present asymmetries that are more likely to inspire nuclear warhead sophistications or stockpile increases among nuclear-armed countries. It is likely, not coincidental, that the Russian strategic nuclear forces have been modernizing over the past several years (according to the September 2008 Secretaries of Defense and Energy paper titled "National Security and Nuclear Weapons in the 21st Century") with new road-mobile and silo-based Topol-M (SS-27) ICBMs; a new SS-27 derivative with multiple, independently targetable, reentry vehicles capability; a new Bulava (SS-30) submarine-launced ballistic missile; a new ballistic missile submarine; and a new long-range strategic nuclear cruise missile designated the KH-102, among others. According to the same source, Russia also explicitly increased emphasis on nuclear weapons in its national security policy and military doctrine.

It has been argued that the U.S. set the example in nuclear disarmament which could result in reciprocal cuts by other nuclear-armed countries. The problem with lead-by-example approaches to disarmament or nonproliferation efforts, all forms, is the inherent nature of self-interested, sovereign countries. When one country achieves a comparative advantage -- in this case conventional military capabilities -- other countries either rebalance the asymmetric relationship or accept the imbalance. When faced with the near impossibility of developing a comparable conventional force, nuclear weapons are the more efficient and effective, if not the only, method of rebalancing the comparative advantage. No country, regime, non-state actor, etc., likes to find itself at a comparative disadvantage, especially if its existence lies in the balance.

In essence, U.S. nuclear forces balance the nuclear equation created by our nation's superior conventional forces, providing them the freedom of maneuver because of our first-class deterrent force. This fact cannot be excluded from any potential adversary's decision-making calculus -- keeping their nuclear option an absolute last resort without hope of victory.