Thucydides was acutely aware of the enduring relevance of his work. In the opening pages of his History of the Peloponnesian War, he writes that he composed it “not as an essay to win the applause of the moment, but as a possession for all time.” His aim was not simply to record the events of the Great War between Athens and Sparta but to illuminate “the future as well”—those patterns that, owing to the constancy of human nature, would recur in similar form.
The proof of that claim is striking. Just last month, Canada’s prime minister Mark Carney invoked the Melian Dialogue in a major speech at Davos to describe the erosion of the rules-based order and the return to an international environment in which “the strong do what they can and the weak suffer what they must.” The reference was not cosmetic—a mere rhetorical flourish. It was a diagnosis of the condition of the international system. The language of power politics has re-entered the mainstream.
This is hardly the first time Thucydides has resurfaced in moments of upheaval. Thomas Hobbes, who translated him into English during the English Civil War, drew heavily on Thucydides’ account of civil strife in Corcyra to describe the descent into lawlessness that follows the collapse of central authority. Hobbes’s conclusion was unequivocal: only a strong state—the “Leviathan”—can secure peace, the precondition of liberty and prosperity.
A century later, British strategic thinkers found in the Athenian naval model of thalassocracy an intellectual precursor to their own maritime empire. During the Cold War, the analogy between Athens and Sparta was frequently deployed to frame the rivalry between the US and the Soviet Union: a democratic sea power confronting a continental, authoritarian land empire.
After Vietnam, American strategists again turned to Thucydides in search of explanations for a defeat that, by conventional metrics of power, seemed improbable. The Sicilian expedition—and the concept of strategic overreach—provided a sobering analogy. From the 1970s onwards, Thucydides became required reading in US war colleges, not as ancient history but as a foundational text of strategic studies, alongside Sun Tzu’s The Art of War and Clausewitz’s On War.
More recently, Thucydides has been enlisted to interpret the intensifying competition between the US and China. The catalyst was Graham Allison’s formulation of the so-called “Thucydides Trap”: the proposition that when a rising power challenges an established one, war becomes highly probable. Conflict may arise either through preventive war—as the dominant power seeks to halt the challenger’s ascent—or through uncontrolled escalation and miscalculation.
This framework, though analytically oversimplified, has exerted considerable influence in policy and academic circles. Invoking Thucydides lent it intellectual authority. Yet the reading that portrays great powers as helpless “sleepwalkers” understates the role of political leadership. Thucydides was not a structural determinist. He recognized the pressures of the international system, but he also assigned decisive weight to the choices of leaders—to prudence or to hubris.
That is the essential lesson. Thucydides did not write his History to prove that war is inevitable. He wrote to show how miscalculation, overconfidence, underestimation of adversaries, ideological blindness, and the loss of restraint can lead to catastrophe.
In the direct democracy of classical Athens, citizens collectively decided questions of war and peace. Political education was not an abstraction; it was a condition of survival. Thucydides’ history functioned as a school of strategic education. Its purpose was to cultivate sophrosyne—prudence: the capacity to recognize the limits of one’s power, to align ends with means, to restrain individual and collective passions, and to think ahead (foresight).
In a world increasingly defined by great-power rivalry and the reassertion of spheres of influence, Thucydides’ relevance is not merely academic. It is political. Structural pressures may push states towards confrontation. But leaders choose. And in periods of profound systemic transition, the absence of prudence is the surest path to tragedy.
