There’s Still No Reason to Think the Kellogg-Briand Pact Accomplished Anything

If Oona Hathaway and Scott Shapiro’s new book The Internationalists: How a Radical Plan to Outlaw War Remade the World is correct, then I’ve been guilty of educational malpractice for the past 30 years. Why? Because I’ve taught a course on “The Origins of Modern Wars” off and on since the 1980s, and one of the cases I address is World War II. In that context, I use the 1928 Kellogg-Briand Pact as an example of misplaced idealism that failed to stop the slide to war and may have made it a bit more likely. In my treatment (and those of many historians and political scientists), the pact — whose signatories agreed to renounce war as an instrument of policy and promised to resolve future disputes solely by “pacific means” — is a mostly irrelevant footnote to history and an object lesson on how not to prevent war.

Not so, say Hathaway and Shapiro. In their view, the Kellogg-Briand Pact was a revolutionary event that ushered out the “Old World Order” where war and conquest were commonplace and legitimate and gave birth to a “New World Order” where war is rare and conquest is even rarer. In their words, “[the peace pact] was among the most transformative events of human history, one that has ultimately made our world far more peaceful. It did not end war between states, but marked the beginning of the end — and with it, the replacement of one international order by another.”

Because I’m always intrigued by new and provocative arguments and try to stay up to date with new interpretations, I turned to Hathaway and Shapiro’s book with considerable interest and curiosity. Do they make a convincing case for their core argument? And do I have to rewrite my lecture on the interwar period the next time I teach that class?

I don’t think so.

Before turning to where I think the book falls short, let me first highlight its virtues. For starters, the book is engagingly written, and much of it is highly entertaining. Hathaway and Shapiro take the reader into areas of 20th-century diplomacy that are all-too-often neglected, and their portraits of key individuals from recent and more distant history — ranging from Hugo Grotius to Carl Schmitt to James Shotwell and more — are at various turns amusing, insightful, and deftly sketched. The book also has the considerable merit of advancing a bold thesis without a lot of defensive hedging, unlike the usual boring monographs that scholars often produce. Hathaway and Shapiro also go to some effort to address alternative explanations and explain why their own argument should be preferred — though, as we shall see, they do not go quite far enough. The bottom line: Reading the book is an enjoyable experience and far from a waste of time.

What is their core argument? Reduced to its essentials, they claim the Peace Pact of 1928 set in motion a far-reaching and ultimately decisive change in the legality and legitimacy of war and conquest. In their view, this shift made it far less likely states would fight and nearly unheard of for them to acquire territory by force. This metamorphosis didn’t take place overnight, but ultimately this change in the collective normative understanding of warfare produced a dramatic and highly consequential change in state behavior.

Hathaway and Shapiro marshal two main bodies of evidence to support this claim. First, they compile an impressive body of data showing that the frequency of interstate war has declined dramatically since the peace pact was signed, precisely as its proponents hoped. Even more tellingly, they show that territorial conquest has become exceedingly rare over the past 80 years. From their perspective, changing borders and incorporating other countries’ territory by force is no longer permissible in the family of nations, and both great and small powers have abandoned the practice for this reason. One result is that small and weaker nations have proliferated and survived, and they no longer need to worry very much about being gobbled up by more powerful neighbors.

They acknowledge that wars still occur and that the use of force has led to territorial expansion in some rare instances. (China in Tibet, Israel in the Golan Heights and West Bank, Russia in Crimea, etc.) But such exceptions pale in comparison to the vast conquests that earlier great powers conducted, conquests that were readily accepted by their counterparts and by the newly conquered peoples as well. At first glance, therefore, their argument seems entirely plausible.

Unfortunately, the evidence Hathaway and Shapiro present does not come close to proving their case. Although they tend to avoid using clear causal language, the novelty of The Internationalists lies in the ambitious causal claim the authors are making. They maintain the peace pact (and the norms it represented) caused a far-reaching change in patterns of warfare. But as we are all taught at the beginning of grad school (if not before) a simple correlation between A and B — in this case between passage of the peace pact and dramatic decline in war and conquest — does not demonstrate that one caused the other.

One reason to be skeptical, of course, is that in the wars that have taken place since the signing of the pact, legal norms didn’t much restrain the battlefield conduct of leaders. Consider the vast devastation the United States wreaked on Indochina from 1964 to 1973 (killing hundreds of thousands of people and poisoning the environment with herbicides), or the vast bloodletting that occurred between Iran and Iraq from 1980 to 1988. Nor have the norms embodied in the peace pact (or the United Nations Charter) prevented great powers like the United States from attacking other countries without prior approval from the U.N. Security Council, even though doing so is a clear violation of international law.

More importantly, even if one accepts their data about the decline of war and conquest — and I do — it does not follow that the Kellogg-Briand Pact was responsible. As legions of scholars have previously argued, the decline in war may be due to the invention of nuclear weapons, which inhibit war by making it both less necessary and more dangerous. Or maybe the cause is rising economic interdependence, because states can now get what they need by trading instead of by taking. It could also be due to the spread of democracy, or even (as John Mueller argued in his book Retreat from Doomsday) due to shifting cultural attitudes about war among the major powers. Or perhaps it is some combination of all of these things. But if so, then why should we conclude the peace pact was the critical ingredient?

To their credit, Hathaway and Shapiro do devote some space to addressing some of these alternatives, and they offer brief accounts for why they do not believe these alternatives fully capture or explain the patterns they observe. But what is really needed is an attempt to weigh the relative impact of these other possible causes against their own preferred choice. It’s entirely possible that the peace pact (and all it entails) “explains” some of the decline in warfare, but how much? Is it 60 percent, 25 percent, 3 percent, or what?

Measuring the relative impact of competing causes is hard, even when one has a lot more data than international relations scholars typically possess. To make their case, Hathaway and Shapiro would have to provide much more detailed historical treatments than they have and show how the mechanism they identify played a critical role in particular decisions for war and peace.

Indeed, what is perhaps most striking about The Internationalists is the absence of clear and direct evidence showing their proposed causal mechanism at work in concrete cases. If changing norms are driving the observed change in behavior, then Hathaway and Shapiro should be able to point to numerous cases where national leaders had a clear incentive to expand their territory and believed it would be easy to do, and then decided not to go ahead either because they believed such an act was inherently wrong or because they were convinced it would never, ever, ever, be accepted by the rest of the international community. Yet as one reads the book, one searches in vain for direct evidence of this sort.

Moreover, there is a simple explanation for the decline in conquest that they do not consider, one that has nothing to do with law, norms, or the peace pact itself. Over the past century, the spread of nationalism from Europe to the periphery and an expanding global supply of small arms has dramatically increased the cost of conquering and subduing a foreign population and then incorporating them within one’s own polity. Once the idea of national self-determination had spread around the globe, local populations were willing to fight and die to expel foreign occupiers, and the spread of small arms and high explosives made it much easier for them to make occupiers pay. The British, French, Dutch, and Portuguese empires all collapsed in good part for this reason, and so did the Soviet Union. Even the mighty United States has been unable to subdue local resistance in places like Iraq and Afghanistan, and Israel was eventually forced to withdraw from southern Lebanon after 18 years.

Meanwhile, as the costs of occupation have increased, the benefits have declined. This trend was already apparent during the Cold War, when the Soviet and American alliance systems together comprised nearly 80 percent of gross world product. With most of the world’s wealth and economic production already aligned on one side or the other, what could either superpower hope to gain by conquering and incorporating some neutral country? Conquering the adversary’s most important allies might have made a difference, but this was far too dangerous to attempt in the nuclear age. Conquering anybody else wasn’t going to change the global balance of power enough to matter, and all the more so when the locals could make you pay a stiff blood price for trying.

From this perspective, the decline in war and conquest has little to do with law or norms — or an obscure treaty signed back in 1928 — and mostly to do with a more straightforward calculus of costs and benefits. Leaders bent on war have to find some way to convince themselves the campaign will be quick and cheap, and after 1945 that usually meant not trying to incorporate and rule unfriendly populations whose resistance would make your life miserable. It also meant not having to grant citizenship to conquered populations of a different nationality or ethnicity, because doing so would eventually create deeper political tensions inside one’s own society.

If this argument is correct, it helps us identify where conquest might still be possible and where borders could still shift. For example, China’s campaign to establish greater territorial control in the South China Sea may eventually succeed because there are hardly any people on those tiny reefs and shoals; asserting Chinese sovereignty in this region does not require Beijing to incorporate and rule a large, sullen and resentful foreign population. Similarly, Russia’s seizure of Crimea may endure because Crimea’s population is mostly ethnic Russians. This fact also suggests that Russian President Vladimir Putin has no interest in grabbing the rest of Ukraine, because trying to govern a lot of angry and resentful Ukrainians would be expensive and difficult.

Last but not least, the conclusion to The Internationalists is at odds with its upbeat thesis. After extolling the virtues of the New World Order and the magnitude of the transformation that Frank B. Kellogg, Aristide Briand, and their descendants supposedly achieved, suddenly Hathaway and Shapiro tell us the present order is delicate and could easily collapse. Having spent several hundred pages highlighting the power of law, norms and collective legitimacy, the real linchpin of the system turns out to be America’s willingness to keep “policing” this order in perpetuity. Norms and law are no longer doing the heavy lifting; it’s our old friend the Pax Americana. Did I hear someone say “indispensable nation”?

Ironically, here Hathaway and Shapiro are echoing neoconservative pundit Charles Krauthammer, who argued back in 2004 that the line between civilization and barbarism “was not parchment but power, and in a unipolar world, American power—wielded, if necessary uniltaterally.” This parallel reminds us of the close kinship between neoconservatism and liberal internationalism, at least on these issues. It’s an alignment that goes a long way to explain the excesses that have bedeviled U.S. foreign policy since the early 1990s and inflicted no small amount of harm on a lot of foreign countries.

To be clear:The Internationalists has a number of virtues, and in many ways I wish their argument were more convincing. As always, that’s what separates realists from idealists: We see the world as it is and they see it as they would like it to be. One day, they may even be right, but for now, I’m going to leave my lecture on interwar idealism pretty much as is.

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