Since the dawn of the nuclear age, a defining feature of US nuclear strategy has been the quest for credible ways to strengthen deterrence -- including the ability to actually win a nuclear war, which of course would reduce constraints imposed on US foreign policy by the spread of nuclear weapons.
During the Cold War, American policy makers worried that the threat of a massive nuclear strike against Soviet cities would lack credibility and even encourage aggression. Moscow might correctly calculate that no American president would launch a nuclear attack -- particularly to defend allies -- knowing that such a strike would in return cause the destruction of the US homeland at the Soviets' hands. In the 1960s, President Richard Nixon and National Security Advisor Henry Kissinger sought to get around this "self-deterrence" problem by developing "limited nuclear options." The idea was that, in signaling to an enemy the limited nature of a nuclear attack, escalation could then be controlled and nuclear threats could be made more credible, thereby buttressing deterrence. Successive presidents have sought to mimic the Nixon administration's efforts to escape the grim reality of deterrence, but, like Nixon, found that they were no less vulnerable than before.
Fast forward to the turn of the millennium and the George W. Bush administration's effort to develop capabilities "to defeat emerging threats such as hard and deeply buried targets (HDBT), to find and attack mobile and relocatable targets, to defeat chemical or biological agents, and to improve accuracy and limit collateral damage." According to the Bush administration, these new capabilities were necessitated by the potential spread of WMD to rogue states and the fact that existing high-yield warheads are ill-suited to deal with post-Cold War threats. Though a Republican-controlled Senate ultimately scuttled these programs, proponents of the US government acquiring the capability to destroy both the nuclear forces and the leaders of smaller nuclear-armed adversaries -- known as "counterforce" -- remain committed and vocal, both inside and outside of government.
Last month, for example, Exchange Monitor Publications and Forums held their fourth annual Nuclear Deterrence Summit, a high-profile conference with participants from across Washington, including a number of former Bush administration and nuclear laboratory officials; they warned of the dangers of self-deterrence and extolled the virtues of low-yield weapons. Similarly, in a much-discussed 2011 Foreign Affairs article, Professors Keir Lieber and Daryl Press argued that US nuclear delivery systems are far more accurate than they were during the Cold War, making it possible to now conduct low-yield successful nuclear counterforce strikes.
The new case for strengthening counterforce. According to Lieber and Press, the spread of nuclear weapons means that the United States will likely find itself in a conventional war with a weaker but nuclear-armed adversary, who, facing a superpower, will have strong incentive to use or threaten to use nuclear weapons to ensure its survival. In these circumstances, an arsenal comprising solely high-yield weapons might not seem flexible enough to avoid massive collateral damage -- and therefore not credible to a 21st-century adversary. Lieber and Press argue that, in order to establish credibility, the United States must retain and modernize its lowest-yield and most accurate weapons in order to destroy an adversary's nuclear forces without mass casualties.
In addition to preventing weaker adversaries from brandishing a nuclear threat, counterforce proponents argue that augmenting low-yield options could deter rogue states from initiating conventional provocations against the United States or its allies. For example, by possessing low-yield counterforce options that could deny North Korea both a nuclear retaliatory capability and its leadership a secure place to hide, the United States would have less to fear from North Korea's conventional incitements -- such as the 2010 attack on the South Korean Cheonan warship. Instead of Americans worrying that a strong US response to such an attack could trigger a dangerous escalation by North Korea, the United States would have more foreign policy options. And, without a secure nuclear retaliatory capability, North Korea may simply be less likely to make such provocations to begin with.
However, like Cold War-era efforts to get around deterrence, these proposals rest on a number of flawed assumptions. As the Obama administration prepares to make critical decisions about the future of the US nuclear arsenal, it would do well to ignore calls to develop new low-yield counterforce options, as they would actually increase the probability of nuclear war and undermine US nonproliferation goals.
The case against strengthening counterforce. Despite low-yield enthusiasts' rhetoric, the United States currently has far more options than launching high-yield weapons against cities. For one thing, the current US nuclear arsenal already consists of a mix of high- and low-yield weapons, giving it the capability to conduct low-yield counterforce strikes. The B-61 air-delivered gravity bomb, for example, has an adjustable yield that can be set very low and can be carried by the stealthy B-2 bomber. The warheads on US cruise missiles can also be set to low yields. But regardless of high- or low-yield weaponry, the truth is that a rogue state or weaker foe contemplating the use of nuclear weapons against the United States would surely understand that such an attack would quickly result in the total destruction of its regime -- whether through the use of conventional weapons, nuclear weapons, or both -- thereby obviating what it hoped to gain through the use of nuclear weapons in the first place. The addition of more low-yield capabilities to the US arsenal would not change this fundamental reality; they are a solution to a deterrence problem that does not exist.
Even if the United States for some reason did want to execute a counterforce strike to preempt an adversary's use of nuclear weapons or limit the damage an adversary's nuclear forces could inflict if deterrence fails, the targets would have to be conveniently located silo-based missiles, bunkers, or other stationary objects. Successfully executing a counterforce strike against mobile or relocatable ballistic missiles is an order of magnitude more difficult. In the all-too-probable event that the United States didn't have excellent intelligence about these targets, it would not be able to effectively destroy them with low-yield weapons. In the case of hard and deeply buried targets, experts have shown that the use of low-yield weapons do in fact cause large amounts of civilian casualties and an adversary could simply dig deeper bunkers. In other words, counterforce hardly adds to the deterrence of nuclear attacks or conventional provocations.
Moreover, these capabilities could actually make the use of nuclear weapons more likely, undermining US nonproliferation goals.
First, in a severe crisis or conventional war, enhanced US counterforce capabilities could prompt an adversary to take destabilizing measures -- like delegate launch authority to field commanders, giving them advance sanction to rapidly launch nuclear weapons should their leaders be killed. While some of these pressures would exist anyway given the potency of existing US forces, adding new capabilities would certainly exacerbate them. New counterforce measures could also lull the United States into an exaggerated sense of invulnerability. A preemptive US counterforce attack that destroyed some but not all of, say, North Korea's nuclear forces would almost certainly trigger North Korea to launch its remaining forces at the United States or its allies -- a risk American leaders should never contemplate.
Second, augmenting US nuclear capabilities would signal a step back in the US effort to reduce reliance on nuclear weapons, particularly if these capabilities required underground nuclear testing. Such a posture could undermine stability with Russia and China, both of which would likely view moves to enhance or expand America's arsenal as a gambit to grease the wheels for a future US offensive military strike. China might also view US nuclear enhancement as a ploy to negate the Chinese deterrent. Pursuit of these capabilities would weaken America's standing in the international community, harming prospects for the global cooperation the United States desperately needs in order to rein in rogue states like North Korea and Iran. In addition, a greater US emphasis on counterforce could prompt other nuclear-armed states to pursue similar capabilities, creating a new kind of arms race. This would be especially destabilizing in South Asia, where India and Pakistan have already fought two conventional conflicts since acquiring nuclear weapons.
US nuclear weapons policy is at a critical crossroad. The administration is currently reviewing future deterrence requirements, which will ultimately revise existing presidential guidance regarding the targeting of nuclear weapons, appropriate force levels, and more. Meanwhile, the Pentagon must decide how, on a tight budget, to replace the land-based missiles, submarines, and bombers that make up the nuclear triad, all of which are nearing the end of their service lives at roughly the same time.
The threats posed by rogue states like North Korea and Iran present real security challenges to the United States, but they can't be addressed by nurturing US nuclear war-fighting capabilities. The United States can easily continue to reduce the role and number of nuclear weapons in its security strategy and still maintain a devastating deterrent without placing greater emphasis on counterforce.