Thucydides, had he lived today, would scarcely have been surprised by the arrogance of great powers or by the geopolitical disorder that now defines international politics. He was, after all, the first to describe with precision the system’s fundamental structural condition: the absence of a central authority capable of imposing rules and guaranteeing order. In such an anarchic environment, particularly under conditions of intense strategic competition, international politics tends to degenerate into a jungle where the only law that matters is the law of power.
The History of the Peloponnesian War is replete with examples showing that, in the absence of effective constraints, the powerful impose their will on the weak without being bound by law, custom, or moral restraint. These are not aberrations but a recurring regularity of a system in which power is the principal currency of international politics. Two of the most revealing instances are Athens’ treatment of Melos and Sparta’s massacre of Plataea. The general conclusion is straightforward: the strong rarely hesitate to dominate the weak when opportunity presents itself and the cost appears manageable.
In the celebrated Melian Dialogue, the Athenians confronted the inhabitants of Melos with a stark ultimatum: submission or war. To arguments grounded in justice and morality, they replied with characteristic cynicism: such arguments carry weight only when adversaries are evenly matched. When power is asymmetric, “the strong do what they can and the weak suffer what they must.”
It was precisely these words that Canadian Prime Minister Mark Carney invoked recently in a landmark speech at Davos to describe the rupture with the past and the end of the post-war international order—an order that rested, however imperfectly, on rules and norms. The world, he argued, is reverting to the language of power politics and geopolitical competition, in which almost any relationship can be weaponized—a “weaponization of everything.”
Lord Acton’s warning still applies: “Power tends to corrupt, and absolute power corrupts absolutely.” Unrestrained power frequently breeds arrogance—but arrogance, in turn, generates resistance. Thucydides makes this point with brutal clarity. Immediately after the Melian Dialogue, he shows how Athenian hubris culminated in the Sicilian Expedition and ended in catastrophe. One of the more durable laws of international politics is that power tends to be balanced by power. This is precisely what occurred in Sicily, where a countervailing coalition formed against Athens.
A pivotal role in this process was played by Hermocrates of Syracuse, who urged Sicily’s medium-sized cities to set aside their rivalries and solve the problem of collective action. If they failed to coordinate, he warned, they would be subjugated one by one. History has largely vindicated his logic: appeasement rarely restrains power; more often it emboldens it.
Today, Carney, in the role of a modern Hermocrates, delivers a similar message to middle powers unsettled by unchecked American power. He urges them not to submit but to coordinate their response and collectively counterbalance pressure. This, however, is easier said than done. States experience threats differently and possess unequal incentives and capabilities. Europe’s reaction to Washington’s rhetoric over Greenland illustrates the point: the French and the Scandinavians raised the banner of resistance, the Eastern Europeans considered the matter none of their concern, while the Germans and the British opted for a more cautious, equivocal posture.
In Sicily, the logic of the balance of power ultimately operated with devastating consequences for Athens. Arrayed against her were not only the Sicilians but also the Spartans and, later, the Persians. The defeat proved decisive for the final outcome of the Peloponnesian War and the collapse of the Athenian empire.
Athens’ downfall was compounded by the gradual erosion of relations with her allies. The Delian League—much like NATO centuries later—was created as a mechanism of collective security against an existential threat. Over time, however, Athens transformed the alliance into something approaching tyranny, a reality Pericles himself acknowledged without euphemism. A comparable dynamic can be observed in NATO today, as the United States adopts an increasingly coercive posture towards its own allies.
Thucydides assigns a considerable share of responsibility to the allies themselves, who neglected their military preparedness and rendered themselves dependent on Athens. America’s European allies followed a similar path, benefiting for decades from the US security umbrella while underinvesting in their own defenses. They now find themselves trapped in a relationship of dependence that Washington is able to exploit.
America’s European allies are confronted simultaneously by military and hybrid threats from Russia, geo-economic competition from China, and political subversion from the United States itself. The imperative of survival—a central concept in Thucydides—typically drives a core of middle-sized powers to seek counter-dependence strategies and balancing. The weaker, by contrast, tend to cling to the hegemon in a posture of bandwagoning, banking on its magnanimity.
Thucydides distilled the motives of state behavior into a triad: fear, interest, and honor. This framework remains strikingly useful for understanding contemporary American strategy. Washington is increasingly anxious about the rapid ascent of Chinese power. For the first time in its history, the United States confronts a strategic rival of comparable scale. China’s economy is already roughly 30 percent larger in purchasing-power terms (PPP); its industrial base and energy production are about twice as large; and its navy is on track to be 50 percent bigger by the end of the decade.
The post-war system—one the US itself constructed—now appears to operate increasingly to China’s advantage. That helps explain why Washington has turned against it. The effort to weaken Beijing begins in the Western Hemisphere, with Venezuela as a telling example, and extends into the Middle East, where Iran is treated as a critical node in a broader Eurasian axis associated with China. In parallel, Washington seeks to draw Russia away from Beijing, a logic that helps explain its accommodating posture on Ukraine.
Interest provides the second motive: consolidating American primacy in the Western Hemisphere and securing control over critical resources, from Venezuelan oil to Greenland’s mineral wealth. Honor supplies the third motive. At a time when rivals portray the US as an empire in irreversible decline, frequent—and often successful—demonstrations of military power serve to reinforce America’s claim to primacy.
Thucydides generally avoids moral judgment. He is concerned with what is, not what ought to be. Yet he is not neutral on political leadership. For him, the supreme virtue of the statesman is sophrosyne—prudence: the capacity to design rational strategy commensurate with the international distribution of power, to master individual and collective passions, and to anticipate the vagaries of fortune (foresight).
Judged by this standard, today’s American leadership would likely invite his skepticism. Reducing commitments in Europe and the Middle East in order to focus on China is intelligible as a prioritization of ends and means. But the systematic antagonization of close allies—Canada, Britain, and Germany—is strategically myopic. It does not weaken America’s adversaries; it strengthens them. In the Peloponnesian War, the fraying of Athens’ alliances benefited Sparta; broader Greek disunity benefited Persia. In much the same way, the present fragmentation of the West works to China’s advantage.
In periods of systemic transition, the quality of leadership becomes decisive. It can multiply power—or squander it. That remains one of Thucydides’ most enduring lessons.
