Wars are not caused by weapons or arms races

My impression is that there has been a lot of both theoretical and empirical research on arms races in the field of international relations, and that this claim is still contested. I therefore find it hard to be confident in this claim.

For example, Siverson and Diehl (p. 214 in Midlarsky, ed., 1989) sardonically note that “[i]f there is any consensus among arms race studies, it is that some arms races lead to war and some do not.” Fifteen years later, Glaser (2004) still opens with:

Are arms races dangerous? This basic international relations question has received extensive attention. A large quantitative empirical literature addresses the consequences of arms races by focusing on whether they correlate with war, but remains divided on the answer.

On one hand, there are several theoretical models that posit mechanisms how arms buildups could causally contribute to wars.

• Security dilemma/spiral model: If states can't distinguish offensive from defensive military capabilities and have incomplete information about each other's goals - in particular, whether they face a "revisionist" state that would seize an opportunity to attack because it wants to acquire more territory -, their desire for security will compel them to engage in a spiral of arming (e.g. Jervis 1978, 2017[1976]). [While commonly cited as a way how arms races could cause wars, I think this idea is somewhat muddy, and in particular it often remains unclear whether the posited mechanism is an irrational stimulus-response cascade or some reason why rational actors would engage in an arms race culminating in a situation where war is a rational response to an external threat. See e.g. Glaser 2000, 2004. Similarly, it's unclear whether even in this model the arms race is a cause of war or rather a mere symptom of underlying structural causes such as incomplete information or states' inability to commit to more cooperative policies; see Fearon 1995 and Diehl & Crescenzi 1998.] A different approach of explaining escalation dynamics culminating in war is Vasquez's (1993) "steps-to-war" theory.
• Costly deterrence: If the opportunity cost of military expenditures required for deterrence becomes too large, and if military spending could be reduced after a successful war, then it can be rational to take one's chances and attack (e.g. Powell 1993, Fearon 2018).
• Preventive war: If a state anticipates that the balance of power would change in an adversary's favor, they might want to attack now (e.g. Levy 1987). Allison (2017) has popularized this idea as Thucidydes's trap and applied it to current US-China relations. The worry that an adversary could acquire a new weapons technology arguably is a special case; as you suggest, the 2003 Iraq War is often seen as an instance, which has inspired a wave of recent scholarship (e.g. Bas & Coe 2012).

On the other hand, there has been extensive empirical research on the arms race-conflict relationship. Stoll (2017) and Mitchell & Pickering (2017) provide good surveys. My takeaway is that the conclusions of early research (e.g. Wallace 1979) should be discarded due to methodological flaws [1], but that some more recent research is interesting. For example, several studies suggest a change in the arms race-war relationship post-WW2, contra your suggestion that the relationship has been similar since at least WW1. Of course, a major limitation is that conclusions are mostly about correlations rather than causation. Some examples (emphases mine):

Gibler, Rider, and Hutchison (2005) add to the literature by addressing a potential selection bias present in many studies. They attribute this to the unit of analysis—a dispute—which presupposes that deterrence has already failed. In an attempt to resolve this, they identify arms races independently of dispute occurrence and use this to test if arms races either deter or escalate MIDs. Using a sample of strategic rival dyads between 1816 and 1993, it was shown that arms races increase the probability of both disputes and war. [Mitchell & Pickering 2017]

Gibler, Rider, and Hutchison (2005) study conventional arms races and war. [...] Only 13 of 79 wars identified by the Correlates of War Project from 1816 through 1992 were preceded by an arms race. As well, only 25 of the 174 strategic rivals identified by Thompson (2001) had an arms race before a war. [Stoll 2017]

Important empirical literature has also placed arms racing in a broader theoretical context to improve comprehension. The “steps-to-war” approach introduced by Vasquez (1993) includes arms races as one of a number factors that contribute to an escalation of violence between states. A good deal of empirical work has tested this approach in the decades since it was first introduced (Colaresi & Thompson, 2005; Senese & Vasquez, 2008; Vasquez, 1996, 2000, 2004, 2009; Vasquez & Henehan, 2001).

[...]

Beginning with Sample’s (2000) multivariate analysis, research on the arms race–war relationship has accounted for territorial disputes and other factors that may influence the outbreak of war. The literature had not, however, examined the relationship between arms races and other steps to war. Vasquez (2004) and Senese and Vasquez (2005, 2008) address this and find that other power politics practices (e.g., alliances and rivalry) do not eliminate the arms race–war relationship.

[...]

Building upon these earlier findings, Sample (2012) conducted another analysis that divided the temporal domain into three separate eras: 1816 to 2001, 1816 to 1944, and 1945 to 2001. She further controlled for state rivalries—dividing the data into disputes within rivalry and disputes outside of rivalry—and used three different measures of rivalry to compare the findings. The results showed that mutual military buildups had a substantial impact on conflict escalation to war, between both rivals and non-rivals. This suggests the relationship between arms races and war is not an artifact of rivalry (see Rider et al., 2011, for a contrary view). [Mitchell & Pickering 2017]

Rider, Findley, and Diehl (2011) [...] also study the relationship between rivalries, arms races, and war. The time period of their study is 1816–2000. They use Diehl’s operationalization of an arms race. They find that taking rivalries into account is important to understanding that relationship. In particular, locked-in rivalries (those rivalries that have experienced a large number of disputes) that experience an arms race are more likely to experience a war. [Stoll 2017]

Endnotes:

[1] E.g. Stoll (2017), emphasis mine:

The broader issue is about the basic research design used by Wallace. He did not examine whether arms races lead to war. He looked at dyads that engaged in militarized interstate disputes and asked whether if prior to the dispute the dyad engaged in rapid military growth. If so, Wallace predicted (and his results—with the caveats of other studies noted above—supported this) that the states were very likely to engage in war.

For the moment let us accept Wallace’s findings. Understanding the conditions under which a dyad that engages in a militarized interstate dispute is more likely to end in war is a contribution to understanding why wars happen. But it does not explain the relationship between arms races and war. Even if we accept Wallace’s index as a valid indicator his research design does not allow for the possibility that there may be many arms races that are not associated with disputes. Including these cases may produce very different conclusions about the linkage between arms races and war.

References:

Allison, G. (2017). Destined for war: can America and China escape Thucydides's trap?. Houghton Mifflin Harcourt.

Bas, M. A., & Coe, A. J. (2012). Arms diffusion and war. Journal of Conflict Resolution, 56(4), 651-674.

Diehl, P. F., & Crescenzi, M. J. (1998). Reconfiguring the arms race-war debate. Journal of Peace Research, 35(1), 111-118.

Fearon, J. D. (1995). Rationalist explanations for war. International organization, 49(3), 379-414.

Fearon, J. D. (2018). Cooperation, conflict, and the costs of Anarchy. International Organization, 72(3), 523-559.

Glaser, C. L. (2000). The causes and consequences of arms races. Annual Review of Political Science, 3(1), 251-276.

Glaser, C. L. (2004). When are arms races dangerous? Rational versus suboptimal arming. International Security, 28(4), 44-84.

Jervis, R. (1978). Cooperation under the security dilemma. World politics, 30(2), 167-214.

Jervis, R. (2017). Perception and Misperception in International Politics: New Edition. Princeton University Press.

Levy, J. S. (1987). Declining power and the preventive motivation for war. World Politics, 40(1), 82-107.

Powell, R. (1993). Guns, butter, and anarchy. American Political Science Review, 87(1), 115-132.

Siverson, R., Diehl, P., & Midlarsky, M. (1989). Handbook of War Studies.

Vasquez, J. A. (1993). The war puzzle (No. 27). Cambridge University Press.

Wallace, M. D. (1979). Arms races and escalation: Some new evidence. Journal of Conflict Resolution, 23(1), 3-16.

If Iran actually does develop something of an atomic arsenal, it will likely find, following the experience of all other states so armed, that the bombs are essentially useless and a very considerable waste of money and effort

This claim strikes me as particularly dubious intuitively. I don't have specific evidence in favor of my intuition, but I think I would want to see quite substantial evidence for Mueller's claim to believe it, as I think my prior is driven by the following considerations:

• At first glance, it seems that Iran's adversaries are also concerned about the prospect of Iran acquiring nukes. For example, the US seems to be willing to pay a substantial cost in terms of tensions with European allies in order to take a tougher stance toward Iran, e.g. the Trump administration cancelling the nuclear deal. Similarly, there clearly were risks involved in deploying the Stuxnet cyber weapon against Iran. (This is an interesting case because Stuxnet was targeted specifically at Iran's nuclear program; so the potential response "Iran's adversaries are using the prospect of a nuclear Iran merely as a pretext to push through policies that hurt Iran more generally, e.g. economically" does not work in this case.)
• More broadly, Mueller essentially seems to claim that there is some very widespread delusion: While in fact nuclear weapons are just a waste of money, all of the following actors are making the same epistemic error of believing the opposite (as indicated by their revealed preferences): most Democrats in the US; most Republicans in the US; most people across the political spectrum in Israel; the government of Saudi Arabia; both "moderate" and conservative politicians in Iran; the government of Russia, etc. What is more, incentives to correct this epistemic error surely aren't super great, but they are not zero either: If, say, a Democratic US President is making a big foreign policy blunder by accepting considerable cost to prevent Iran from acquiring nuclear weapons, why aren't there more Republicans who jump onto this opportunity to embarrass the government? Why is the prospect of a nuclear Iran able to - at least to some extent - unite a diverse set of actors such as the US, the EU, Israel, Saudi Arabia, and Russia behind a common foreign policy objective, i.e., to prevent Iran from acquiring nuclear weapons?
• I also think the claim flies in the face of common sense. In particular, Israel is a tiny country in a vulnerable geographic position, it has been attacked several times since its inception, and Iran has consistently taken a very hostile stance toward it (and not just via cheap talk, but also by e.g. sponsoring insurgent groups in Lebanon). At first glance, I find the suggestion that the additional option of (explicit or implicit) nuclear threats against Israel would not hurt Israel's interests hard to believe. Similarly, the US has a history of recent interference in Middle Eastern countries via conventional wars, see Afghanistan and Iraq. I think an American attack on Iran with the objective of regime change within the next decade is at least plausible, and everyone knows this. On the other hand, I don't think anyone has ever tried to attack a nuclear weapons state with a regime change objective. (AFAIK the only direct military conflicts between nuclear weapons states were a 1969 border conflict between China and the USSR, and the 1999 Kargil War between India and Pakistan - both cases in which all sides clearly had much more limited objectives.) Again, I think the idea that the US would invade an Iran armed with nuclear weapons is on its face implausible. If this is true, then possessing nuclear weapons would decrease one of the arguably major risks to Iranian sovereignty - so how can they be a "considerable waste of money and effort"?

I understand that you mostly just provide a summary rather than giving reasons to believe the claims in the book, but FWIW I find some of the claims hard to believe. I'll give more detail in other comments.

For now, some general questions:

• What kind of evidence is the book based on? (E.g. archival research, interviews with decision-makers, theoretical models, ...)
• Does Mueller have a credible debunking explanation for why most people in the national security community (as well as fields such as international relations, nuclear strategy etc., AFAICT) disagree with him?

It is likely that no “loose nukes” — nuclear weapons missing from their proper storage locations and available for purchase in some way — exist

This squares well with my weakly held prior, based on crude beliefs such that most dangers around terrorism are exaggerated.

However, I'm wondering how Mueller treats the question of whether we would know. E.g., during a 2007 incident in the US, several nuclear weapons were mistakenly loaded onto a bomber that was unguarded for hours at both its start and target locations; no-one realized the weapons were missing for about 36 hours, and the whole problem was only discovered once someone discovered the nukes in the bomber.

My guess is that nuclear weapons handling procedures would probably have uncovered eventually that some warheads were missing at the storage location. But as this incident illustrates it's (i) unclear when, and (ii) there is room for human error (according to Schlosser's Command and Control, the incident was only possible because four different crews failed to check whether the relevant missiles were loaded with nuclear warheads, even though all of them were supposed to).

Also note that there were a very small number (2-5 based on a loose memory) of accidents in which nuclear weapons were lost and, as far as we know, never recovered. E.g., over Canada in 1950, and in the sea near Japan in 1965. Of course, most likely these weapons haven't been discovered by anyone, and thus are not "available for purchase".

So while "likely" seems plausible to me, I find it hard to have extreme confidence in there being no "loose nukes".

More relevantly, I'd hope that Mueller discusses all of these cases, or else I'd decrease my confidence in his claims.

On the deterrence effect of nuclear weapons, I think the following empirical finding is interesting. (Though not conclusive, as this kind of research design cannot establish causality.)

Sample (2000) found that arms races increase the chances of both MIDs [militarized interstate disputes] and the likelihood that an MID will escalate to full-scale war. However, she discovered that this was only the case in disputes that occurred before World War II. Similarly, territorial disputes were no longer found to be associated with escalation in the post–World War II era. Sample suggested that the presence of nuclear weapons was a possible explanation for why arms races in the post-war era were found to be less likely to result in the outbreak of war than those that occurred prior. She introduced a nuclear weapons variable to test this and found that the probability of war decreased to .05 when nuclear weapons were present during a mutual military buildup. Sample’s discovery of the potential pacifying effect of nuclear weapons was an important contribution to our understanding of how quantitative and qualitative arms race–war relationships differ.

Quote from Mitchell and Pickering, 2017, an encyclopedia article reviewing work on arms races (emphasis mine). On the impact of nukes, they continue (emphasis mine):

The advent of nuclear weapons thus appears to have changed the arms race–conflict relationship. It is important to note in this regard that many policymakers seem to place nuclear weapons in a different conceptual category than conventional weapons. As Sagan (1996, p. 55) has argued, nuclear weapons “are more than tools of national security; they are political objects of considerable importance in domestic debates and internal bureaucratic struggles and can also serve as international normative symbols of modernity and identity.” There have also been attempts to explain “nuclear reversal” cases by which states forgo or give up on their programs (Campbell et al., 2004; Levite, 2003; Paul, 2000; Reiss, 1995; Rublee, 2009). Research has shown that the possession of such weapons is contingent upon both willingness and opportunity (Jo & Gartzke, 2007). While security concerns and technological capabilities are significant determinants of whether states pursue the development of nuclear weapons, the possession of such weapons is dependent upon such factors as domestic politics and international considerations (Jo & Gartzke, 2007). Furthermore, states are heavily dependent upon sensitive nuclear assistance from more advanced nuclear states when attempting to develop a nuclear arsenal (Kroenig, 2009a, 2009b).2 The nature of nuclear weapons acquisition is thus multifaceted and may not always be motivated by arms races. Once acquired, however, nuclear capabilities seem to impact the likelihood of conflict escalation and disputes between states.

[...]

[Gibler et al. 2005] controlled for several variables previously demonstrated to be predictors of conflict in a dyad. Among these was the joint presence of nuclear weapons, which was shown to prevent the outbreak of war (as no war has occurred in a dyad where both states possessed nuclear weapons). However, if both states had nuclear weapons, this was found to actually increase the probability of MID onset. Subsequent research has shown that nuclear dyads have engaged in a large number of militarized disputes short of war and may be even more likely to engage in MIDs than non-nuclear states or asymmetric pairs of states (see, e.g., Beardsley & Asal, 2009; Rauchhaus, 2009).

Gibler et al.’s (2005) discovery that nuclear dyads are less likely to engage in all-out war between rivals but more likely to engage in MIDs and hostile action short of war contributes to the broader understanding of the role nuclear weapons play in state decisions to use military force. Although a detailed discussion of nuclear deterrence is outside the scope of this article, it is important to highlight a key debate within this context. Among those who believe that nuclear weapons can serve as a deterrent (often referred to as “proliferation optimists”), some have argued that possession can deter aggression at all levels (Jervis, 1989; Waltz, 1990). Others, meanwhile, have contested that possession secures states from high-level conflict escalation (e.g., war) but increasingly contributes to lower-level hostile action (e.g., MIDs) (Snyder, 1965; Snyder & Diesing, 1977). This concept is known as the “stability-instability paradox,” which states that “to the extent that the military balance is stable at the level of all-out nuclear war, it will become less stable at lower levels of violence” (Jervis, 1984, p. 31).

I haven't read this book and I'm also not an expert, so my confidence on this comment is low.

But-

Although nuclear weapons seem to have at best a quite limited substantive impact on actual historical events, they have had a tremendous influence on our agonies and obsessions, inspiring desperate rhetoric, extravagant theorizing, wasteful expenditure, and frenetic diplomatic posturing

Not only have nuclear weapons failed to be of much value in military conflicts, they also do not seem to have helped a nuclear country to swing its weight or “dominate” an area

Wars are not caused by weapons or arms races, and the quest to control nuclear weapons has mostly been an exercise in irrelevance

As a relative layman, I find claims like these puzzling. This is primarily because the "agonies and obsessions ... desperate rhetoric, extravagant theorizing, wasteful expenditure, and frenetic diplomatic posturing" that Mueller apparently dismisses drove the course of history for the half-century following the Second World War.

It's hard to imagine that the Cold War would have occurred at all in the absence of nuclear weapons. While it's true that the first nukes didn't pose much more serious a threat than a large-scale firebombing, it was barely more than a decade after the war that much more destructive weapons were being built. A successful conventional Soviet assault on the U.S. mainland was, as far as I know, never a serious possibility. It seems clear that the terror of that period was driven by the nuclear threat, and that the nuclear threat drove U.S. and Soviet strategic posture, which also influenced foreign aid, trade policy, etc. Even if their danger is exaggerated, perception of their danger (in my view an unavoidable perception--even the Joint Chiefs were prepared to nuke Cuba during the missile crisis despite knowing that the strategic situation had not appreciably changed) had serious effects.

Also, and again, not an expert (and I'd like to know if Mueller addresses this specific case) but of course Israel has been a nuclear power since as early as 1979. Before that date, Israel fought three major wars and dozens of smaller engagements with its neighbors. Since then, virtually all of Israel's military conflicts have been essentially counterinsurgency or against state proxies such as Hezbollah. It's often argued that Israel's status as a nuclear power has driven Iran's efforts in that arena, which has also influenced Saudi belligerence; this conflict has affected oil prices, domestic politics in both countries, the ongoing war in Yemen, etc. This is kind of a long DAG, but I feel like there are other examples like this, and I find it sort of hard to accept the position that the simple existence of nuclear weapons hasn't been immensely consequential.

(2) I continue to worry that the so-far (apparently) perfect safety and security record for nuclear weapons will eventually end, which could (but probably won't) have global catastrophic effects

My guess is you're very likely aware of this, but for other readers it might be worth pointing out that the safety record is "perfect" only if the outcome of interest is a nuclear detonation.

There were, however, several accidents where the conventional explosives (that would trigger a nuclear detonation in intended use cases) in a nuclear weapon detonated (but where safety features prevented a nuclear detonation). E.g., accidents involving bombers in 1958 and 1968, the latter also causing radioactive contamination of an uninhabited part of Greenland; and some accidents involving missiles, e.g. in 1980. See also Wikipedia's list of military nuclear accidents.

More broadly, the sense I got e.g. from Schlosser's book Command and Control is that within the US government and military it was a contested issue how much to weigh safety versus cost and desired military capabilities such as readiness. The book mentions several individuals working in government or at nuclear weapon manufacturers campaigning for additional safety measures or changes of risky policies, with mixed success - overall it seemed to me that the US arsenal did for decades contain weapons for which we at least couldn't rule out an accidental nuclear detonation with extreme confidence.

(Similar remarks apply to security. I forgot the details, but it doesn't inspire confidence that senior US decision-makers on some occasions worried about scenarios in which European allies such as Turkey might seize scarcely guarded US nuclear weapons during a crisis.)

Thanks for posting these notes. 

In case this is useful to anyone, here's a 1-hour talk + Q&A the author did about the topic of the book. I found parts of the talk interesting, though to be honest much of the reasoning seemed poor to me.

(I haven't read the book myself.)