Letters to the Editor

Dear Editor:

Since the beginning of the nuclear weapons age, there has been a continuous “intellectual;” dispute between advocates of “nuclear war” and of “nuclear deterrence”. Equivalently, the dispute is between the reliance upon “counter force” technology—relying upon increasing missile accuracy, knowledge of target locations, and C3I—and “counter value technology—relying upon survivability of the retaliatory forces. Over the years the U.S. has developed both capabilities, though its publically issued governmental policies have more frequently emphasized “MAD” – mutually assured deterrence”. Lieber and Press cite increasing capabilities of required counterforce technology to seemingly press for a decreasing emphasis on nuclear weapon limitation and an increase of reliance on counter force security policies because of their seemingly increased ability to wipe out the retaliatory weapons required for effective deterrence. (They do admit that such a re-emphasis on counter force can be a significant threat to global security.) However, it should be noted that nowhere in their article do they establish significant threats to the SLBM force—the retaliatory missiles constantly prowling deep underwater in the Earth’s vast oceans. Nothing in their vaunted C3I improvements, given the known laws of physics, will be able to hinder a devastating retaliatory blow following any possible counter force attack on the existing SLBM forces which will survive. Thus their apparent call for a re-emphasis on counter force strategies, with consequent de-emphasis on nuclear arms limitation efforts, is not only dangerous to world stability but unnecessary for our national security—which should continue to depend upon MAD (Mutually Assured Destruction).

Alvin M. Saperstein
Wayne State University

Dear Editor,

In the January issue, Keir A. Lieber and Daryl G. Press argue that emerging technologies are creating a “New Era of Nuclear Arsenal Vulnerability.” We share the authors’ interest in how new technologies can influence nuclear security, but we are not convinced that critical shifts have occurred or are inexorably on their way.

The longest section of Lieber and Press’s article recounts how missile accuracy has improved since the 1980s, making hardened missile silos more vulnerable to attack. Here the technical point is credible, but the strategic importance is limited. Only the US and Russia keep a significant fraction of their nuclear weapons in silos, and their vulnerability has been recognized for decades. This is one reason why nuclear weapons are deployed on submarines, land-based mobile launchers, and bombers, which maintain a retaliatory capability largely immune to the “accuracy revolution.”

The burden of the authors’ argument thus falls to the “sensor revolution,” where the technical discussion is much weaker. This section amounts to a catalog of broad “technological trends,” all on the side of “seekers.” While it is reasonable to predict that sensors and their platforms will improve, so will the tactics and technologies that counter them. Weapons platforms will diversify, potentially to autonomous systems, networked sensors may grow more vulnerable to electronic warfare, and anti-satellite capabilities will advance. Without a comparative analysis between hiders and seekers, we are not persuaded by the authors’ suggestion that seekers will gain the edge.

Statements about the growing effectiveness of conventional weapons against nuclear forces (e.g., “conventional weapons can destroy most types of counterforce targets”) are also too broad and unsupported to take at face value.

Certainly many types of technology are improving, but it does not follow that a dramatically new era is dawning. Demonstrating that new technologies will “undercut the logic of future nuclear arms reductions” and make arms racing “nearly inevitable” would, in our view, require much stronger evidence than Lieber and Press provide.


Rachel Carr
Department of Physics
Massachusetts Institute of Technology

Thomas D. MacDonald
Department of Nuclear Science and Engineering
Massachusetts Institute of Technology

The computer revolution has transformed nearly every aspect of our world. In “The New Era of Nuclear Arsenal Vulnerability” we describe how the dramatic improvements in guidance systems and remote sensing are making nuclear forces more vulnerable to disarming strikes, and hence complicating the mission of deterrence.1

Alvin Saperstein shares our concern that efforts to exploit these new “counterforce” improving technologies may trigger dangerous arms races, but his call to deemphasize such capabilities overlooks two factors: First, effective counterforce capabilities could be extraordinarily valuable if an adversary (such as North Korea) began to threaten or employ nuclear weapons during a war. Second, counterforce capabilities—including improved sensors, better command and control systems, and pinpoint-strike weapons—will be developed by the United States to enhance U.S. conventional forces. As long as the United States is committed to fielding the most powerful conventional forces in the world, it will deploy capabilities that also render adversary nuclear arsenals vulnerable.

Saperstein also believes that concerns over arsenal vulnerability are overblown because submarines are inherently secure. This was not true in the past, however, and we doubt it will be true in the future. There were periods of the Cold War in which the United States trailed every deployed Soviet ballistic missile submarine.2 Today the United States is building a new generation of submarines that must not merely evade the sensors that Russia and China deploy today, but also those that will be developed over the next 30-40 years, a daunting challenge given the rapid pace of technological change. The problem for Russian and Chinese submarines is even greater, given the United States’ technological lead in undersea warfare and ongoing investments in those areas.

Rachel Carr and Thomas MacDonald note that although hardened sites are growing more vulnerable, few countries rely on missile silos to protect their nuclear forces. However, many nuclear-armed states store their aircraft and mobile missiles in hardened shelters, protect their weapons in reinforced bunkers, and control their arsenals from hardened command sites. Those facilities would be prime targets in any disarming strike. Moreover, as accuracy continues to improve, hardened sites are becoming more vulnerable to the lower-yield nuclear weapons that the United States and other countries are developing, as well as to conventional strikes.

Carr and MacDonald also note that countermeasures can foil efforts to locate or strike nuclear targets. We agree, and for this reason we believe that countries with considerable resources, such as the United States, will have an easier time keeping nuclear forces secure than poorer and technologically limited countries. Our point is that the computer revolution has transformed the competition between “hiders” and “seekers.” A few decades ago, the job of mobile missile operators was simpler, because there were few feasible means for adversaries to monitor large deployment areas, especially those deep in one’s own territory. Today, mobile missile operators have a much tougher job: for example, with timing their moves to avoid expanding constellations of radar satellites, countering unattended ground sensors, and anticipating and blocking all the other means of locating mobile forces.

In 1980, John Steinbruner and Thomas Garwin punctured the fears, popular in that era, about the vulnerability of strategic nuclear arsenals.3 Their analysis identified a set of technological breakthroughs that would have to occur for nuclear forces to become susceptible to disarming strikes. That seminal article is worth rereading today, because each of those technological breakthroughs—and many more—have become reality.

The strategic deterrence community has grown complacent. Almost every aspect of the nuclear deterrence equation has changed since the Cold War: weapons are more accurate, sensors are more effective, and now target sets are far smaller. It would be strange if all the old “truths” about nuclear deterrence remained valid despite these revolutionary changes. Coming to terms with the reality of a new era of nuclear arsenal vulnerability is the first step toward a better understanding of the global political and strategic implications.

Keir A. Lieber, Georgetown University
Daryl G. Press, Dartmouth College
March 1, 2018


1 Keir A. Lieber and Daryl G. Press, “The New Era of Nuclear Arsenal Vulnerability,” Physics and Society, Vol. 47, No. 1 (January 2018), pp. 2-5. The longer, more technical version of the argument appears in Keir A. Lieber and Daryl G. Press, “The New Era of Counterforce: Technological Change and the Future of Nuclear Deterrence,” International Security, Vol. 41, No. 4 (Spring 2017), pp. 9-49, (https://www.mitpressjournals.org/doi/abs/10.1162/ISEC_a_00273).

2 See See Austin Long and Brendan Rittenhouse Green, “Stalking the Secure Second Strike: Intelligence, Counterforce, and Nuclear Strategy,” Journal of Strategic Studies, Vol. 38, Nos. 1–2 (2015), pp. 38–73; Owen R. Coté Jr., The Third Battle: Innovation in the U.S. Navy’s Silent Cold War Struggle with Soviet Submarines (Newport, R.I.: Naval War College, 2003); and Peter Sasgen, Stalking the Red Bear: The True Story of a U.S. Cold War Submarine’s Covert Operations against the Soviet Union (New York: St. Martin’s, 2009). See also our discussion in Lieber and Press, “The New Era of Counterforce,” pp. 35-37.

3 John D. Steinbruner and Thomas M. Garwin, “Strategic Vulnerability: The Balance between Prudence and Paranoia,” International Security, Vol. 1, No. 1 (Summer 1976), pp. 138–181.

These contributions have not been peer-refereed. They represent solely the view(s) of the author(s) and not necessarily the view of APS.