My second claim is that while war is the worst imaginable way to create larger, more peaceful societies, it is pretty much the only way humans have found. “Lord knows, there’s got to be a better way,” Edwin Starr sang, but apparently there isn’t. If the Roman Empire could have been created without killing millions of Gauls and Greeks, if the United States could have been built without killing millions of Native Americans—in these cases and countless others, if conflicts could have been resolved by discussion instead of force, humanity could have had the benefits of larger societies without paying such a high cost. But that did not happen. It is a depressing thought, but the evidence again seems clear. People hardly ever give up their freedom, including their rights to kill and impoverish each other, unless forced to do so, and virtually the only force strong enough to bring this about has been defeat in war or fear that such a defeat is imminent.

My third conclusion is that as well as making people safer, the larger societies created by war have also—again, over the long run—made us richer. Peace created the conditions for economic growth and rising living standards. This process too has been messy and uneven: the winners of wars regularly go on rampages of rape and plunder, selling thousands of survivors into slavery and stealing their land. The losers may be left impoverished for generations. It is a terrible, ugly business. And yet, with the passage of time—maybe decades, maybe centuries—the creation of a bigger society tends to make everyone, the descendants of victors and vanquished alike, better off. The long-term pattern is again unmistakable. By creating larger societies, stronger governments, and greater security, war has enriched the world.

When we put these three claims together, only one conclusion is possible. War has produced bigger societies, ruled by stronger governments, which have imposed peace and created the preconditions for prosperity. Ten thousand years ago, there were only about 6 million people on earth. On average they lived about 30 years and supported themselves on the equivalent of less than two modern American dollars per day. Now there are more than a thousand times as many of us (7 billion, in fact), living more than twice as long (the global average is 67 years), and earning more than a dozen times as much (today the global average is $25 per day).

War, then, has been good for something—so good, in fact, that my fourth argument is that war is now putting itself out of business. For millennia, war has created peace, and destruction has created wealth, but in our own age humanity has gotten so good at fighting—our weapons so destructive, our organizations so efficient—that war is beginning to make further war of this kind impossible. Had events gone differently that night in 1983—had Petrov panicked, had the general secretary actually pushed the button, and had a billion of us been killed over the next few weeks—the twentieth century’s rate of violent death would have soared back into Stone Age territory, and had the toxic legacy of all those warheads been as terrible as some scientists feared, by now there might have been no humans left at all.