GAZETTE: How would you characterize relations between China and the United States today as compared with, say, the 1970s under President Richard Nixon?

ALLISON: What most Americans still haven’t awakened to is that just in the last generation [China] has emerged like a rocket to displace the U.S. as the No. 1 producer of automobiles, computers, smartphones, and artificial intelligence. Indeed, it’s the largest economy in the world as measured by the best yardstick for comparing national economies: purchasing power parity. In the book, I illustrate this in terms of a seesaw, in which the U.S. is on one end and China is on the other. If you go back to 1990, China had about 15 percent the weight of the U.S. By 2014, China is roughly equal with the U.S., and by 2024 will be half again larger. So, just in our lifetime, a state that hardly mattered in international affairs and hardly mattered as a buyer or seller of anything has emerged as a serious rival and, in many arenas, has surpassed us.

GAZETTE: Can you explain Thucydides’ Trap? What prompted you to consider U.S.-China relations through this lens, and how does it help?

ALLISON: Thucydides’ Trap is the dangerous dynamic that occurs when a rising power threatens to displace a ruling power. That dynamic creates structural conditions in which events by third parties or accidents that would otherwise be inconsequential or manageable can in fact cascade to consequences that nobody wanted or could imagine. The insight comes from Thucydides in his great history of the Peloponnesian War. He wrote about the competition between the two leading city-states in classical Greece. In probably the most quoted one-liner in international relations study, he wrote, “It was the rise of Athens and the fear that this instilled in Sparta that made the war inevitable.”

You’ve got two variables here: the objective condition of the rise of Power A relative to Power B, and then a subjective condition, which is the perception of that, especially by the ruling power. In the past 500 years, I’ve found there have been 16 cases in which a rising power threatens to displace a ruling power. In 12 of these, the outcome was war. In four, the outcome was not war.

Think about the rise of Germany 100 years ago and the fear that this instilled in Britain. If one asks: How is it conceivable that the assassination of an archduke who would have been successor to the throne in Austria-Hungary becomes the match that lights a fire that, by its end, has burned down all of the European houses? The answer is this occurs in the context of this Thucydidean dynamic. Because it’s fearful of a rising Germany, Britain enters into entanglements which it had rigorously resisted with both Russia and France. And Germany, having only one ally, feels required to back its weakling Austrian-Hungarian empire. Otherwise it would have no allies. So an event that would have otherwise been manageable comes to create a conflagration.

As I argue in the book, at the end of World War I in 1918, what happened to the things that all of the principal actors cared about most? The answer is, they had lost them. The Austrian-Hungarian emperor [“relinquish(ed) every participation in the administration of the State”] and his empire is dissolved. The Russian czar who’s backing the Serbians has been overthrown by the Bolsheviks, so he’s lost his whole regime. The Kaiser in Germany has been dismissed. The French have been bled for a whole generation. And Britain has been shorn of its treasure and its youth and turned into a debtor when before it had been a creditor. So if you’d given a chance to any of these parties for a do-over, nobody would’ve made the decisions that they made. But they were made, and that was the outcome.

So the application to the case of China and the United States today is that no sane person in the U.S. government thinks a war with China is a good idea. Similarly, I don’t believe there’s anybody in China who matters who thinks a war with the U.S. is a good idea. Does that mean war cannot happen? The answer is it does not. But if we look at our histories, we discover that despite the fact that people have the right perception that a war would be catastrophic for their interests, they nonetheless may find themselves making choices in which they are prepared to tolerate risks they normally wouldn’t if they were not caught up in the grips of the dynamics of Thucydides.

Take the Cuban missile crisis and its analogue unfolding today with North Korea. In the missile crisis, Kennedy was prepared to run a 1-in-3 chance of a nuclear war that could kill 100 million people to prevent the Soviet Union from placing nuclear missiles in Cuba. When he got into the middle of this crisis, and especially as he got to the end, he began to have second thoughts. I think as we watch what’s likely to happen over the next year in North Korea, we’re going to see what level of risk of a war Trump will accept to prevent North Korea from being able to launch a nuclear warhead against Los Angeles or San Francisco. I don’t believe it will be less than what Kennedy was prepared to run as a risk. And if you think about it, that’s terrifying. ...