The Deliberate Employment of US Nuclear Weapons: Escalation Triggers on the Korean Peninsula

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ABSTRACT

This paper focuses on the conditions under which the United States might use nuclear weapons during a war on the Korean Peninsula. It identifies several circumstances that might trigger such a decision, the purposes of a US nuclear strike, and the plausible targets. Attention is focused on the roles that nuclear weapons continue to play in US military operations and foreign policy strategy despite steps to reduce their salience since the end of the Cold War. I argue that the United States would only consider using nuclear weapons if (1) the mission being performed was of critical importance, (2) it could not be accomplished with sufficient certainty or speed with non-nuclear options, and (3) the use of nuclear munitions significantly increased the probability of success. This paper identifies a range of circumstances that could arise during a war in Korea that might satisfy all three criteria, and it identifies the pathways that are most likely to trigger US nuclear employment. Examining these conditions now can help US allies and other partners identify and resolve disagreements about nuclear employment, enhance deterrence against regional adversaries, and shed light on the logic driving important decisions about US nuclear force structure and modernization.

KEYWORDS:

• Nuclear-weapon use
• escalation
• United States
• Korean Peninsula
• DPRK

Disclosure Statement

No potential conflict of interest was reported by the author(s). This paper is prepared for Reducing the Risk of Nuclear Weapons Use in Northeast Asia (NU-NEA), a project co-sponsored by Research Center for Nuclear Weapons Abolition, Nagasaki University (RECNA), Asia Pacific Leadership Network for Nuclear Non-Proliferation and Disarmament (APLN) and Nautilus Institute with collaboration of Panel on Peace and Security of Northeast Asia (PSNA). Additional funding is provided by the MacArthur Foundation.

Notes

¹ Unauthorized nuclear employment refers to a circumstance in which military personnel (or others entrusted with the weapons) use them without valid authority. In peacetime those dangers are minimized by material barriers (such as locks) and procedures that govern the handling of the weapons. Some of those protections, however, may be weakened during a nuclear crisis (in order to increase the readiness and survivability of the nuclear forces). Accidental detonations (as opposed to unauthorized use) refer to instances in which nuclear weapons are detonated without any actor deliberately choosing to release them – for example, the result of a crashed aircraft carrying nuclear weapons, or a fire at a storage site. Modern US nuclear weapons are designed to minimize the probability of accidental detonation, but the possibility of accidental detonations cannot be fully ruled out for any country’s arsenal.

² In fact, the Biden Administration is reportedly considering adopting a “sole use” policy for US nuclear weapons, which (if enacted) would limit the role of US nuclear forces to deterring or responding to adversary nuclear employment (Sonne and Hudson 2021).

³ As will become clearer later in this paper, these three criteria (e.g. the importance of the mission, and the need for nuclear munitions to accomplish it) do not necessarily refer to a mission with military importance. Some of the most important potential triggers for US nuclear employment are rooted in the perceived geopolitical importance of US nuclear retaliation after various adversary actions.

⁴ Furthermore, as Paul Davis and Bruce Bennett point out in another article in this supplement issue, geopolitical events that seem implausible do happen – and given the stakes involved, planners and analysts should at least consider the possibility of a reckless invasion by the DPRK.

⁵ On military missions associated with these problems see Bennett and Lind (2011).

⁶ Among the best unclassified analyses of the risk that DPRK artillery poses to ROK cities are Barnett et al. (2020); Gentile et al. (2019); Cavazos (2012).

⁷ The DPRK has also apparently built some number of extensive underground facilities near the DMZ (“subterranean complex battle positions”), which would allow their forces to fight from within heavily protected fortifications (US Department of the Army 2020, 37–41). It is unlikely, however, that the DPRK’s long-range artillery (i.e. the ones that can strike Seoul) can fire from within these structures. The concussive effects of firing very large caliber guns inside structures would likely incapacitate DPRK artillerymen, and the backblast from large rocket launchers would be extremely dangerous in a confined space. I thank Joseph Bermudez for helpful discussions on these points.

⁸ For an excellent analysis of the consequences of varying levels of North Korean artillery attack on the ROK, see Barnett et al. (2020).

⁹ Nuclear weapons that are detonated as “air bursts” – meaning at a high enough altitude to prevent the debris from the ground from mixing with the fireball – produce very little fallout, allowing nuclear strikes to occur without causing much collateral damage. For an analysis of the relationship between warhead yield, target hardness, height of detonation, and fallout in the context of the Korean Peninsula, see Lieber and Press (2017, 28–32).

¹⁰ In the 1970s and 1980s, NATO planned to do exactly this to blunt a Warsaw Pact invasion of Western Europe. The United States and its allies envisioned using “theater nuclear weapons” against second-echelon Warsaw Pact forces, plus nuclear strikes on Warsaw Pact supply depots, rail yards, and bridges, to destroy the forward momentum of an offensive.

¹¹ A recent RAND analysis of future US artillery requirements states in passing that in the process of fighting a conventional war, US and ROK forces would conduct strikes aimed to “neutralize [DPRK] WMD capabilities” (Gordon et al. 2019, 34–35). Gordon et al.’s view is consistent with unclassified interviews I conducted with USFK and CFC war planners in 2013, who suggested that air strikes against DPRK WMD (including nuclear sites) was a major part of CFC conventional military plans for war on the Peninsula (Lieber and Press 2013a).

¹² Of the many ways in which the DPRK’s economy appears ill-prepared to support a sustained conventional war against the South, perhaps the most critical is Pyongyang’s shortfalls in stocks of petroleum products (Hayes and von Hippel 2017).

¹³ By detonating nuclear weapons as “airbursts” (that is, at sufficiently high altitude that the fireball does not mix with debris from the ground), the DPRK could destroy ROK military forces without creating fallout, which would impede a DPRK military advance.

¹⁴ Facing conventional military defeat, DPRK leaders would face life-and-death incentives to use nuclear weapons to coerce the CFC to accept an immediate ceasefire. The potential targets for initial DPRK attacks in such a scenario are wide ranging: the first DPRK coercive move could be a nuclear demonstration over its own territory, a detonation over the sea, an attack on a military installation in the ROK, or even an attack on a small city. What distinguishes “defensive coercion” as an escalation strategy is not the target, per se, but the coercive intent. The purpose would be to use nuclear weapons in a manner that demonstrates that additional escalation is likely, and then to issue a clear threat: halt the offensive military operations immediately or suffer further nuclear attacks. On coercive nuclear escalation, see (Lieber and Press 2009, 2013b).

¹⁵ By launching a major counterforce campaign, the CFC will inadvertently create another incentive for the DPRK to use WMD and in particular nuclear weapons to coerce the CFC to immediately halt their counterforce strikes. That said, if CFC planners expect that DPRK WMD escalation is very likely (for the three reasons described above), they may logically conclude they must degrade DPRK WMD capabilities as much as possible.

¹⁶ Unclassified estimates of key DPRK sites vary substantially, but given inevitable target identification uncertainty, CFC / STRATCOM planners will presumably strike confirmed targets, likely targets, and maybe even possible targets as a way to ensure that their strikes damage as many actual critical WMD sites as possible.

¹⁷ It is essential to remember that if DPRK nuclear escalation appears likely (e.g. because their conventional forces are collapsing, because their political leaders are issuing nuclear threats, and/or because certain forces or NC3 systems are alerted), a CFC disarming strike would not need to be completely successful to save millions of lives. A counterforce strike that destroyed seventy-five percent of intended targets might destroy all DPRK nuclear delivery systems (or create a mismatch between surviving delivery systems and surviving weapons). Furthermore, given the questionable reliability of DPRK missiles and warheads (and the possibility of successful missile defense), a few surviving DPRK weapons may not result in any successful retaliatory strikes. The overarching point is that faced with likely DPRK escalation, even imperfect counterforce options may be appealing and logical – and such strikes may require some number of nuclear weapons.

¹⁸ It is difficult to place biological weapons on this continuum because they vary enormously in their consequences, from non-contagious and non-lethal pathogens to highly contagious lethal ones.

¹⁹ Among the many reports of the decay of the DPRK military over the past decade, see Shim (2017); Persio (2017); Silver (2020); Bernal (2021). For a summary of the state of DPRK weapons, see Kim (2020b). That report notes that most of North Korea’s ground force weapon systems are either from the middle decades of the Cold War or are built based on those obsolete designs. To put this in context, the condition of the DPRK army seems comparable to the condition of the front-line, conscript infantry that Saddam Hussein deployed along the Kuwait-Saudi border in 1990. Whereas Iraq’s well-armed and well-trained Republican Guard fought bravely (though ineffectively) against the US-led coalition, the front-line infantry – armed with obsolete weapons, lacking basic maintenance, denied training, and deprived of healthy food – collapsed immediately. A DPRK leader considering ordering a major offensive would need to confront the real possibility that his army might immediately collapse upon first contact.

²⁰ Some analysts worry that although the DPRK military may be in terrible condition overall, elements of their forces (for example, the missile forces) may have higher levels of training, maintenance, and morale. Even if true, the ability of the DPRK to execute a successful invasion of the South, triggering the United States to consider nuclear strikes on second echelon forces, depends on the preparedness of the DPRK military overall – not simply elements such as the missile forces.

²¹ Even if the DPRK used WMD to cause a breakthrough in CFC lines, it is debatable whether nuclear strikes on second echelon forces would be an effective way to stall a DPRK offensive. Skeptics argue that tactical nuclear weapons would have too small a lethal radius to inflict sufficient damage on DPRK follow-on-forces or supply lines, given that they can disperse to reduce their vulnerability to attack. I would counter that the United States has a wide range of nuclear yields available for such a contingency (e.g. from the various configurations of B-61s, W-76s, and W-88s), and that an airburst attack (to avoid fallout) could create chaos and shortages in an DPRK army that would already be operating with minimal supplies. More analysis of this potentially important questions is merited. For an excellent analysis that takes the “skeptical” stance on nuclear strikes on second echelon forces, see Bryan et al. (1978) and see the helpful discussion of this issue in Hayes (2014).

²² The expectation, common among United States Forces Korea (USFK) planners, that the DPRK will use WMD early during a war on the Peninsula is based on (a) assessments that without such attacks, the DPRK would have little hope of battlefield success against strong CFC forces and (b) the repeated threats of the DPRK leadership to do exactly this.

²³ Unclassified interviews I conducted with USFK and CFC war planners a decade ago confirmed that, at least then, air and missile strikes on DPRK WMD sites were core elements of CFC conventional war plans. See Lieber and Press (2013a); and Lieber and Press (2013b).

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Daryl G. Press

Daryl G. Press is an associate professor of Government at Dartmouth College. His work focuses on US foreign policy, deterrence, and the future of warfare. He has published numerous articles and two books: Calculating Credibility (2005), which examines how leaders assess credibility during crises, and The Myth of the Nuclear Revolution: Power Politics in the Atomic Age (2020), which explores deterrence challenges of the 21^st century. Press worked as a consultant at the RAND Corporation for nearly twenty years, and he has taught classes on conventional force modeling for two decades. His work has appeared in leading academic journals as well as in the popular press including Foreign Affairs, The New York Times, and The Atlantic Monthly.