Consider the worst-case scenario.  

I have argued here before that the global situation today more closely resembles the 1970s than any other recent period. We are in something like a new cold war. We already had an inflation problem. The war in Ukraine is like the Arab states’ attack on Israel in 1973 or the Soviet invasion of Afghanistan in 1979. The economic impact of the war on energy and food prices is creating a risk of stagflation.

But suppose it’s not 1979 but 1939, as the historian Sean McMeekin has argued? Of course, Ukraine’s position is much better than Poland’s in 1939. Western weapons are reaching Ukraine; they did not get to Poland after Nazi Germany’s invasion. Ukraine faces only a threat from Russia; Poland was partitioned between Hitler and Stalin.

On the other hand, if one thinks of World War II as an agglomeration of multiple wars, the parallel starts to look more plausible. The U.S. and its allies must contemplate not one but three geopolitical crises, which could all happen in swift succession, just as the war in Eastern Europe was preceded by Japan’s war against China, and was followed by Hitler’s war on Western Europe in 1940, and Japan’s war on the U.S. and the European empires in Asia in 1941. If China were to launch an invasion of Taiwan next year, and war were to break out between Iran and its increasingly aligned regional foes — the Arab states and Israel — then we might well have to start talking about World War III, rather than just Cold War II.

How would you feel if you seriously thought World War III was approaching? As a teenager, I avidly read Sartre’s trilogy about French intellectuals on the eve and outbreak of World War II, the first volume of which is “The Age of Reason.” I remember being haunted by the feeling of existential angst that beset his characters. (In a metaphor that memorably conveys the nihilism of prewar Paris, the protagonist Mathieu’s first thought on learning that his mistress Marcelle is pregnant is how to procure an abortion.) It is the summer of 1938, and impending doom looms over everyone.

I had not thought about those books for many years. They only came back to me after the Russian invasion of Ukraine on Feb. 24 because I recognized with a shudder that feeling of inexorably approaching catastrophe. Even now, after five weeks of war notable for the heroic success of the Ukrainian defenders against the Russian invaders, I still cannot quite rid myself of the uneasy feeling that this is merely the opening act of a much larger tragedy. 

The last time I was in Kyiv, in early September last year, I made a bet with the Harvard psychologist Steven Pinker. My wager was that “by the end this decade, Dec. 31, 2029, a conventional or nuclear war will claim at least a million lives.” I fervently hope I lose the bet. But mine was and is not an irrational angst. As I sat in Kyiv, pondering Vladimir Putin’s likely intentions and Ukraine’s vulnerability, I could see war coming. And war in Ukraine has a track record of being very bloody indeed.

Since the publication of his book “The Better Angels of Our Nature” in 2012, Pinker and I have argued about whether the world is getting more peaceful — to be precise, whether there has been a meaningful trend for war to become less frequent and less deadly. The data he draws on for that book (in chapters 5 and 6) certainly make it look that way.