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Matthew A. Sears is professor of classics at the University of New Brunswick.

In his monumental history of the Peloponnesian War between Athens and Sparta, the ancient Greek historian Thucydides argued that while the conflict had many proximate causes, the ultimate cause was the growth of Athenian power and the fear this caused in Sparta. Athens – the expansionist upstart, in Thucydides’s telling – threatened to unseat Sparta from its traditional position of supremacy, driving the Greeks inexorably toward war in 431 BC. This, in short, is what scholars have since called “the Thucydides Trap”: the theory that an established power and a rising power will almost necessarily go to war with each other.

Graham Allison, a political science professor at Harvard University, has studied the Thucydides Trap, and in 2015, he concluded that despite a few outlying cases, Thucydides’s analysis was prescient, applying to many conflicts beyond that ancient Greek example, including between the United States and China. As he argued, only an extraordinary effort on both sides, and an abandonment of traditional measures such as containment, can prevent a new global war.

That conflict may still be on the horizon. But recent events in Eastern Europe have awakened us all to the possibility of armed conflict among the world’s greatest militaries and has reignited anxieties that have lain dormant since the fall of the Soviet Union. Russian President Vladimir Putin’s invasion of Ukraine threatens to spark a new war in Europe that looks very much like the old wars in Europe, and it has led many of us to wonder whether the relative peace we have enjoyed over the past decades was an aberration, and whether war really is inevitable.

That realization may have felt particularly shocking because so many of us in the West have been lulled into a sense of security. Despite conflicts in places such as the Balkans, the Middle East and East Africa, we have largely been shielded from the threat of widespread war over the course of the 1990s. That feeling of invulnerability was abruptly shattered on 9/11, but even then, the conflicts that followed were fought – from the perspective of the West at least – by professional militaries instead of citizen conscripts. It did not feel as if we were really all within war’s reach, even though so many others around the world have understood this, all along.

But simply accepting war as an inherent part of the human condition – to accept that business-as-usual between and within two rivalling powers is a trap that will lead to bloodshed – can itself make avoidable war a self-fulfilling prophecy.

Take that early example, from Thucydides’s work. While he did provide penetrating insights into the motivations of individuals and states – each time I teach him to undergraduates, we are all struck by how prophetic he was – Thucydides also sometimes contorted characters and events to fit his neat theories. Indeed, he was a revisionist historian, seeking to combat popular beliefs about the Peloponnesian War and playing down the culpability of the Athenian leader Pericles, whom Thucydides admired. If the Peloponnesian War was destined to happen, individual actors and states are largely absolved of their own responsibility, by Thucydides’s reckoning.

Thucydides is one of the most influential authors of Greek antiquity because his work has shaped so many scholarly fields, from ancient history to modern international relations. But we have access to other sources for the Peloponnesian War that suggest some of Thucydides’s impressive propositions might rest on faulty foundations.

The comic playwright Aristophanes and the biographer Plutarch, for example, blame Pericles for the war, and suggest that his reckless pursuit of Athenian expansion was designed to offend Sparta and spark a destructive showdown. They even imply that Pericles’s hawkishness stemmed from a desire to distract from financial scandals in which he was involved. In other words, it seemed that there were policy options available to Athenians eager to assert their influence, and some of them might not have led to war.

While there is no neat correlation between today’s belligerents and Sparta and Athens, we can recognize many of the same behaviours as those pervasive in Greece 2,500 years ago – Thucydides, after all, got a lot right about humans and states. Still, we should critique his all-too-neat analysis, lest it drive us to fatalism. Thucydides viewed war as a destabilizing force that destroys human lives and human character: this much is true. He might be wrong, however, about its inevitability.

Mr. Putin’s condemnable invasion of Ukraine, and the human suffering it has caused, is indefensible. Countries in Eastern Europe have a right to their autonomy, and should not have to live in fear of the Kremlin and its armies. But NATO and the EU have expanded into Eastern Europe in a way that has worried many Russians, not just Mr. Putin – just as Athens did throughout the Aegean Sea, at Sparta’s expense. And NATO and its allies do not have an unblemished track record when it comes to supporting imperialism in various parts of the world; key NATO powers have initiated illegal wars of their own, such as the 2003 invasion of Iraq. Which is to say: we can all work to change things. Business as usual just won’t cut it; to believe it will, is to fall into Thucydides’s trap.

As David Graeber and David Wengrow’s sensational new book, The Dawn of Everything, demonstrates, our view of history is remarkably brief and parochial, even if we look back as far as the ancient Greeks. Humans have found many different ways to live with each other in the world, and not all of those ways feature endemic warfare. Perhaps it’s time to read Thucydides’s History as a cautionary tale – not of the inevitability of war itself, but as an exploration of the dire consequences that follow from such a belief.

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