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In the last ten years, there has been an explosion of quantitative research on nuclear weapons. The basic structure of these models is to compare a variety of conflict outcomes across dyads of different types: those in which both countries have nuclear weapons, those in which neither has nuclear weapons and asymmetric dyads in which one country is a nuclear power and the other isn’t. Conflict outcomes are measured in a variety of ways, from machine-coded capture of diplomatic interactions, to various levels of militarized disputes, to outright conflict and war.
The relevance to those studying the Korean peninsula would at first blush appear obvious. There are a number of strategic interactions that could in theory be modeled this way, most notably the relationship between the US and North Korea (moving from an asymmetric dyad to one in which North Korea has a nuclear capability) and North and South Korea (which moved from one of conventional parity—or even Southern dominance—to an asymmetric dyad after North Korea’s first test). But at the outset it is worth noting several fundamental limitations of these models for understanding the Korean peninsula. Clearly, this is a much more complicated game than can be captured in simple dyadic interactions with China, US alliances and extended deterrence all coming into play; new research is now turning to network effects to capture these complexities. And while the data on the nuclear era has become richer with the passage of time and the accumulation of cases, we are still dealing with relatively rare events from which it can be difficult to draw firm inferences.
Caveats aside, for those with access to an academic library, Erik Gartzke (UCSD) and Matthew Kroenig (Georgetown) have written a useful review of this sometimes-frustrating literature for the Annual Review of Political Science. The frustration comes from the fact that the answers to the biggest questions often appear inconclusive if not downright contradictory.
For nuclear optimists, there is evidence that nuclear weapons may have a dampening effect on crises; Asal & Beardsley (2007) find that crises involving nuclear weapons states are less likely to end in violence. But there is also evidence provided by Rauchhaus (2009) for the so-called stability-instability paradox, long visible between North and South on the peninsula as a result of stable conventional deterrence. Rauchhaus finds that while war is less likely between dyads in which both possess nuclear weapons, low-level conflict is more likely when at least one state possesses nuclear weapons. Horowitz (2009) finds that there may be temporal effects, however, that young nuclear powers flex their muscles and are significantly more likely to become embroiled in militarized controversies. Over time, however, these effects diminish, perhaps as a result of learning or greater confidence in the deterrent.
These findings are closely related to the debate about the utility of nuclear weapons that I have reported on before with respect to Korea. Kroenig (2013) himself has written a controversial essay to the effect that nuclear superiority can increase the risks that states run in crisis bargaining, a finding relevant both to North-South relations and US interactions with North Korea. Beardsley and Asal (2009) also find that nuclear actors are more likely to prevail when facing a non-nuclear state. But Sechser & Fuhrmann (2013) found that nuclear weapons did not assist states in compelling adversaries, certainly a lesson that would appear to emerge out of the long unsuccessful efforts of the US to get the North to abandon its weapons program.
Another area of particular interest has to do with the dynamics of proliferation. In one of the more robust findings in this small literature, there does not appear to be much evidence for the proposition of cascades or contagion: the idea that if a country like North Korea proliferates, its neighbors will follow. This may have to do with a second finding: that formal nuclear commitments both increase the credibility of extended deterrence (Bleek and Lorber 2014) and that alliance commitments reduce the likelihood that alliance partners will proliferate. These findings are clearly relevant to Donald Trump's pronouncements on Northeast Asia.
However, Kroenig (2016) shows that this relationship does not work in reverse, and particularly with the United States; there is no evidence that reductions in the size of the American nuclear arsenal had any effect on the propensity of states to proliferate. President Obama’s trip to Hiroshima will no doubt try to revive his flagging nuclear agenda, but even were the US to be able to make commitments to reduce its nuclear arsenal, it is highly doubtful that these would have any effect whatsoever on North Korea’s nuclear march (for reviews of these capabilities, see our analysis here and here).
Many of these studies are based on dichotomous coding of nuclear status—not taking into account either the depth of the arsenal or force posture. Narang (2013) notes that mere acquisition of nuclear weapons may not be enough to deter conventional conflict. But a posture of asymmetric escalation appears to have such an effect, which might explain why North Korea is so intent on signaling its willingness to use its weapons: precisely because they understand that merely having a few devices may not be adequate.
In 2009, Alexander Montgomery and Scott Sagan published a critique of this quantitative literature that highlighted a standard set of problems with such work from the quality of the data to the fact that the more robust findings were often those that were most obvious. Yet with a much longer history of the nuclear age behind us, there is no good reason not to take this literature on board when thinking about the Korean peninsula. If there is a logic to nuclear weapons, it is certainly worth the effort to figure out what it is.
Articles cited in this piece:
Asal V, Beardsley K. 2007. Proliferation and international crisis behavior. J. Peace Res. 44(2):139–55
Bleek PC, Lorber EB. 2014. Security guarantees and allied nuclear proliferation. Journal of Conflict Resolution 58(3):429–54
Horowitz MC. 2009. The spread of nuclear weapons and international conflict: Does experience matter? Journal of Conflict Resolution. 53(2):234–57
Kroenig M. 2013. Nuclear superiority and the balance of resolve: explaining nuclear crisis outcomes. International Organization. 67(1):141–71
Kroenig M. 2016. U.S. nuclear weapons and nonproliferation: Is there a link? Journal of Peace Research. In press
Narang V. 2013. What does it take to deter? Regional power nuclear postures and international conflict. Journal of Conflict Resolution. 57(3):478–508
Rauchhaus RW. 2009. Evaluating the nuclear peace hypothesis: a quantitative approach. Journal of Conflict Resolution. 53(2):258–77
Sechser TS, Fuhrmann M. 2013. Crisis bargaining and nuclear blackmail. International Organization. 67(1):173–95
