The idea of "Global Zero" has returned to the public agenda, referring to the total elimination of nuclear weapons. On the surface this idea is very appealing. Global Zero was proposed in a Wall Street Journal Op Ed by four prominent former officials, two Republican and two Democrats: George P. Shultz, William J. Perry, Henry A. Kissinger and Sam Nunn on January 4, 2007 with a similar call for the total elimination of nuclear weapons by Mikhail Gorbachev on January 31, 2007 and a renewed call by the original group of four on January 15, 2008.
Global Zero has the support of the Obama Administration and was the subject of President Obama's April 5, 2009 speech in Prague following a joint statement of Presidents Obama and Medvedev committing their two countries to achieving a nuclear free world." On the surface this idea is appealing. It is hard to imagine what could be wrong with a policy to eliminate nuclear warheads whose only purpose is either to kill tens of thousands of people or to destroy an opponent's nuclear warheads. Paradoxically, however, a world without nuclear weapons could be one that is very dangerous and unstable. It is our belief that one way to make Global Zero possible is for the United States to invest in developing a non-nuclear response to a nation that acquires a small number of nuclear weapons and uses the existence of these weapons to extort economic or political concessions, such as in the current world situation North Korea and potentially Iran. One possible way to do this is to deploy a weapon such as the Conventional Trident Modification (CTM) Program. As we will argue, Trident missiles carrying non-nuclear kinetic warheads could deter a country from clandestinely attempting to acquire, deploy and then use a small number of nuclear weapons for political purposes.
There is a very technical literature that was primarily motivated by the Cold War, and some of the results of this body of work are applicable to the current global situation. One of the more important results is that the probability of war is high in a conflict situation where the parties have very few nuclear weapons, or even worse, where only one of the parties has even a few such weapons, which was the only situation in which such weapons were used, by the U.S. against Japan in 1945. During the Cold War, this observation led to the doctrine of Mutual Assured Destruction or "MAD". As a result, both sides invested in a large number ICBM, bomber and missile-carrying submarines so as to have a survivable second- strike capability.
It may be possible to negotiate a treaty to eliminate nuclear weapons, however it is impossible to eliminate the technology for the manufacture of nuclear weapons and the knowledge of how to do this that is widespread and available on the Internet. Given current technology, a country with a stockpile of fissile material could be able to produce nuclear weapons in a matter of months. In a situation where no country has nuclear weapons, a rogue country could clandestinely produce a small number of weapons, given. Most of the technology needed to produce such weapons is dual-use, involving both civilian and potential military use. Thus the boundary between the capability needed to produce nuclear weapons and having such weapons has been blurred. There have been recent attempts to change the threshold from the actual acquisition of nuclear weapons that is banned by the Nuclear Nonproliferation Treaty, to the acquisition of the capability to construct nuclear weapons. This is difficult, however, since the exact boundary that differentiates general knowledge from knowledge specific to producing nuclear weapons is not well defined and it becomes less defined as technology progresses. Furthermore, technical change will continue to progress. Computers will continue to become more powerful, and computer-controlled machine tools will become more common and less expensive. The only substantial barrier to building nuclear weapons may be access to fissile material. If climate change lead to an increased dependence in nuclear power then it may become more difficult to restrict access to fissile material.
MAD worked during the Cold War. We will never know whether the doctrine was sound or we were just lucky. If the doctrine worked, it required a high degree of rationality and sophistication on the part of the nations involved. This may not be the case if among the processors of nuclear weapons is a politically unstable rogue state. This creates a dilemma: In a world where nuclear weapons are eliminated, a country may be tempted to clandestinely build a small stockpile of nuclear weapons for bargaining purposes. We believe, however, that there may be a way to avoid this dilemma. It may not be possible to prevent a nation state from having the capability to build nuclear weapons. We believe, however, that it is possible to develop non-nuclear weapons systems that are credible and powerful enough to serve as an effective deterrent to any nation contemplating building a small number of nuclear weapons to extort political or economic concessions. Such as system would initially serve as a deterrent to nuclear proliferation and may, in fact, make Global Zero stable.
Credibility is crucial in this area. The very elements that may have made the MAD doctrine viable reduce its credibility vis-à-vis a rogue nuclear nation. It is no longer credible that the United States or any of the major powers would use nuclear weapons to retaliate against the infrastructure and population of a rogue nation that used or threaten to use nuclear weapons. Nuclear weapons have only been used at the end of WWII, by the U.S. against Japan. The decision to drop two atomic bombs in Japan is still a subject of considerable controversy. It was, however, in many ways, a logical extension of existing practices of the time. The atomic bomb was seen as a means to destroy the enemy's cities, industries, and, especially, its will to fight. The bomb did what was already being done using conventional weapons by both sides in the war. In fact, more people were killed in the firebomb raids on Tokyo than by both atomic bombs. The special horrors and the threat to the human gene pool and the environment associated with radiation were not known or well understood at the time.
After the war, the scientific and military communities as well as moral and political philosophers pondered the implications of nuclear weapons. It became clear that nuclear weapons were not a very effective means for a nation to use in pursuit of its political and economic objectives. It became necessary to develop complicated and sophisticated strategic doctrines so as to rationalize the acquisition and deployment of these weapons. Ultimately, it was seen by Bernard Brodie, Carl Kaysen, and others that the role of nuclear weapons was primarily to deter their use by other nations.
Although weapons designers eventually developed warheads that were "clean" and potentially useful on the battlefield as tactical nuclear weapons, the concept of a nuclear threshold that could not be crossed except at a high cost became ingrained in the strategic thinking of the mid-twentieth century. The nuclear threshold was so well defined and accepted that a small and poor country like North Vietnam was able to inflict a political defeat on the United States without fear of its use of nuclear weapons. Nuclear weapons did not prove to be an effective instrument of war or policy, whether by the United States in Vietnam or by the Soviet Union in Afghanistan or currently by the U.S. in Iraq and Afghanistan.
The existence of a large stockpile of United States nuclear weapons was not a credible deterrent to their political use by minor rogue nuclear powers. In 1985 we first proposed that the U.S. reconfigure submarine-launched ballistic missiles with conventional warheads that could provide a non-nuclear deterrent that was politically credible. In 2002, together with another coauthor, we wrote a paper published by the Baker Institute at Rice University that proposed that the United States reconfigure some of its Trident II missiles to deliver kinetic energy warheads. (Anyone interested in the details of the proposal can find it on the Baker Institute website.) That proposal was sent to the Office of the Secretary of Defense. In 2006 the Department of Defense received funding to start to develop such a weapon in the Conventional Trident Modification (CTM) Program. The proposal differed from ours in two very important ways. First, the warheads are smaller to extend the range and, second, only a few missiles in any ballistic missile submarine would be conventional. Thus the missiles submarines would be carrying would be including both conventional and nuclear warheads.
Congress has objected to the deployment of the CTM is that it could be destabilizing, as it would be impossible to differentiate between the launch of a conventional weapon and nuclear weapon. This could, indeed, be a problem if the Navy deploys submarines with a mix of nuclear and conventionally-armed missiles and launches from a location normally associated with the patrol area of submarines carrying nuclear missiles in a deterrence role. This would also require that the warhead have the same weight as the nuclear payload because it would not be possible to reduce its range.
Our proposal differs in that we argue that all the missiles on a submarine be converted to CTM missiles and thus the submarines could be deployed closer to the possible targets and use larger warheads. The trajectories of a missile launch from a CTM submarine would be different from that of a nuclear-armed missile boat on patrol. Few, if any of our potential adversaries have any significant anti-submarine capability, so it would be possible to move the submarines close to their coast prior to attacking, constituting an effective deterrent.
If the submarines were only carrying non-nuclear warheads, then it would be in the interest of the United States could allow other major nuclear powers to verify that the submarine was carrying non-nuclear warheads. It would be in the interest of the United States to make public - within limits - the location of the submarine. It should be remembered that the role of a CTM missile submarine would be very different from the role of a missile submarine whose mission is to insure the survivability of the United States second-strike capability. Rather, as a show of force, a potential adversary should know that conventionally-armed submarines are on patrol in the immediate vicinity. Congress commissioned the National Academy of Science to do a study of the CTM and in that study, its 2008 report stated:
Major Finding 1. There are credible scenarios in which the United States could gain meaningful political and strategic advantages by being able to strike with conventional weapons important targets that could not be attacked rapidly by currently deployed military assets. In light of the appropriately extreme reluctance to use nuclear weapons, conventional prompt global strike (CPGS) could be of particular value in some important scenarios in that it would eliminate the dilemma of having to choose between responding to a sudden threat either by using nuclear weapons or by not responding at all.
We believe that if the Navy is willing to dedicate some of its nuclear submarines to a CTM role and eliminate the ambiguity that has troubled members of Congress, then we should fund the deployment of the CTM. This not only reduces the value of a few nuclear weapons to a rogue state, it also makes possible the stability of Global Zero in the future.