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Insights from the Past: Thucydides on Great Power Competition

Thucydides’ History of the Peloponnesian War is more than an account of conflict between Greek city states. It is a thoughtful analysis of one of history’s earliest recorded great power rivalries. The U.S. Department of Defense is openly recalibrating American national security to focus on great power competition.[1] In that context, Thucydides remains a source of enduring utility.

Convinced of the immutability of human nature, Thucydides believed the events he described could “happen again at some time in the same or a similar pattern.”[2] A successor, the Greek historian Polybius, echoed this sentiment, writing that any lesson removed from history “is of no enduring value for the future.”[3]

This article identifies five insights from Thucydides to help us understand enduring lessons about great power competition. First, great powers are constantly looking for new partners and fear losing existing friends and allies. Second, within the context of great power competition, geopolitical alignments and power are dynamic. Third, great power competition is a long-haul business with an uneven trajectory. Fourth, new actors are likely to enter great power competitions and expand the contests into new theaters. And fifth, great power conflicts are always costly, even for the victor. These lessons have enduring relevance for present-day great powers, such as the United States and China.


In Thucydides, an internal dispute in the city-state of Epidamnus is a key spark for conflict. One Epidamnian faction appealed to Corcyra, the city-state which founded Epidamnus. The other side appealed, in turn, to Corcyra’s founder, Corinth. Corinth was Sparta’s most powerful ally. Worried they would be overwhelmed in a coming clash with Corinth, the Corcyraeans appealed to neutral Athens for assistance. Athens, one of the most powerful states in the ancient Greek world, agreed to a defensive alliance with Corcyra despite knowing confrontation with Corinth meant the risk of war with Sparta.

Uneasy in its relationship with Sparta and Corinth, Athenian policymakers were convinced that adding Corcyra, which possessed the third largest fleet in the Greek world, as an ally was a good idea. In the context of these competitions, Athenians feared a Corinthian victory would add Corcyra’s power to the Spartan side, eroding their naval supremacy.[4]

Corinth pressed its campaign against Corcyra, in spite of the potential for conflict with Athens, but was defeated. In defeat, Corinth appealed to Sparta to declare war on Athens. This approach was critical because the Corinthians threatened to “turn in desperation to some other alliance” if Sparta did not support them in their conflict with Athens.[5] Corinth was the most powerful of Sparta’s allies; its importance and its centrality to Sparta’s alliance structure, compelled Sparta to intervene.[6]

Representatives of Athens and Corinth at the Court of Archidamas, King of Sparta, from the History of the Peloponnesian War by Thucydides (Hans Leonhard Schäufelein/Wikimedia)

When great powers compete, the importance of their allies is heightened. Spurred by Corinth’s threats, the Spartan assembly decided the Athenians had violated the terms of their treaty and declared war on Athens. Corinth’s defection from the Spartan alliance was a credible threat because of the second insight we may derive from Thucydides—in the world of great power competition, alignments and power are dynamic.


Competing great powers work to bring about realignments within the international system. China, for example, undermines American influence and extends its own through economic inroads into Europe, the Belt and Road initiative, its closer relations with Russia, and its massive investments in Africa.

Thucydides’ claim that the war was caused by “the growth of Athenian power and Spartan fear of it” has spawned variations on hegemonic transition theory.[7] Graham Allison’s ersatz Thucydides Trap is a recent example. Allison postulates,“When a rising power threatens to displace a ruling power, alarm bells should sound: danger ahead.”[8] Logically sound, this advice highlights the danger of a potential showdown because of the growth and decline of relative levels of power. It does not, however, offer an analysis of how and why such a future showdown might occur. Most critically, it ignores the fact that power defies easy measurement, forcing us to analyze more closely what we consider a rising power as opposed to an established one.

Allison’s simplification paints the United States as a ruling power soon to be displaced by a rising China. In Allison’s Thucydides Trap, Athens is the rising challenger and Sparta the dominant hegemon. This synthesis is challenged by Thucydides himself, who writes that “much of Greece [was] already subject to Athens.”[9] In Thucydides, we see that Athens, not Sparta, acted like a hegemon, dominating trade, expanding territorially, and constantly increasing its wealth and power. Sparta, in contrast, is reactive almost to the point of inertia.[10] These realities muddle the simple logic of a rising power challenging an established hegemon and suggest that measuring who is more powerful among great powers is not a simple exercise.[11]

Comparing Chinese and American power today is not straightforward, as studies like the one presented by Brooks and Wohlforth have made clear.[12] In military terms, America’s fifth generation aircraft, 11-2 superiority in aircraft carriers, and stockpile of nuclear weapons have done very little to prevent China from pushing forward its plans to dominate the South China Sea. In economic terms, the United States remains the world’s largest economy, $21.43 trillion at the end of 2019.[13] But that economy is wracked with trade deficits, nearly $853 billion in 2019, an enormous national debt—more than $25 trillion in early 2020—and personal debts totaling $14 trillion.[14] The American economy is larger that China’s, but how much more powerful is it? In terms of purchasing power, China’s economy is already larger than that of the United States.[15] China had a trade surplus of $421.9 billion in 2019, and the supply chains of many wealthy American companies depend on Chinese production.[16]

Ambiguity in the distribution of economic power between the United States and China is demonstrated in the inability of either state to use their economic (or military) power to win a trade war or favorably resolve a number of existing geopolitical disputes. The difficulty in comprehending and measuring power in a dynamic world leads us to Thucydides’s third insight regarding great power competition. In part because power remains dynamic and difficult to measure, states often misjudge their ability to achieve their desired outcomes leading to drawn out conflict.


Precisely because power between great power competitors is dynamic and difficult to measure, conflict and escalation do not guarantee a swift and favorable outcome. Conflict often proceeds in fits and starts, and in ways quite different from policymakers’ predictions.

Both Athens and Sparta were jolted by unexpected setbacks in their momentous conflict. During the second year of the war, Athens was struck by a plague that killed perhaps a quarter of the city’s population.[17] The Spartans were shocked by their defeat at Pylos and the surrender of 292 hoplites, including 120 Spartan peers at Sphacteria.[18] Advantage shifted from one power to the other and back again.

In spite of the image of a single, continuous struggle, Athens and Sparta made peace in 421 BCE. The terms of the Peace of Nicias were largely favorable to Athens, since Athens retained its dominance within the Delian League and its supremacy at sea. Corinth and Sparta led the outbreak of war in 431, but Athenian policymakers looked to undermine the peace of 421, pursuing the creation of an anti-Spartan coalition with Argos in 420 and finding themselves opposing Spartan forces in battle in 418 at Mantinea.

"Destruction of the Athenian Army in Sicily" by Hermann Vogel, showing the final defeat of the Athenian at the river Assinarus. (Eon Images)

In 415, with the Peace of Nicias still in force, hawkish Athenian policymakers decided to sail for Sicily in the hopes of conquering the island and using its resources to triumph in a final contest with Sparta. This projection was wildly optimistic. The Athenian failure before the walls of Syracuse set Athens on the road to its final defeat. Even so, the Athenians refused a Spartan peace offer based on the status quo in 406, less than a year before their critical defeat at the battle of Aegospotami.[19]

In Thucydides, we see both the conflict and its duration subject to domestic political battles, changes in the geopolitical landscape, and even unanticipated events of enormous disruptive power like the Athenian plague.


Because competition between great powers is often drawn out, the competition is likely to spread beyond the great powers themselves as they seek ways to improve their relative positions. Earlier, we noted the Athenian decision to accept neutral Corcyra as an ally brought Athens into conflict with Sparta’s ally Corinth. Once the war began, the Spartans were under no illusions they would be able to confront the Athenians at sea with their existing coalition. They attempted to raise 500 ships in Italy to confront Athens. “Both sides,” Thucydides tells us, “had plans to send embassies to the King of Persia and elsewhere in the barbarian world where they hoped they might gain support.”[20] In 420, the Athenians allied with Sparta’s rival Argos (which was neutral at the time) with the goal of ending Spartan dominance in the Peloponnese. And, of course, Athens expanded the war westward through its attack on Syracuse.

The ongoing competition between China and the United States also exhibits expansive tendencies. Tense fronts in the relationship between the United States and China now include sovereignty in the South China Sea, mineral rights and loans in Africa, American intellectual property, and trade agreements with European partners. America has taken notice of closer ties between China and Russia.[21] China is aware of America’s overtures to India.[22]

Expanding the conflict is often fundamental to its result. Sparta was able to defeat Athens, in large part, because it brought new powers to its side. Athens was defeated in its assault on Syracuse, and the Athenians failed to match the strength of Sparta’s alliance. However, Sparta’s victory was not achieved without great cost and did not establish a peaceful new world order devoid of conflict.

Meeting between the Persian prince Cyrus the Younger and the Spartan general Lysander (Francesco Antonio Grue/Wikimedia)


Athens’ defeat holds another lesson for great power competition, one largely ignored when we look at conflict between the United States and China. Rising powers often lose the military contest against the hegemon. And victorious hegemons emerge wounded, sometimes fatally. The war between Athens and Sparta, and its aftermath, demonstrate that victory in a great power competition is not achieved without cost nor is it maintained without effort.

Sparta suffered significant casualties and incurred substantial costs. Relations with its allies, notably Corinth and Thebes were strained. Corinthian and Theban leaders even suggested the destruction of Athens and the enslavement of its population. Sparta demurred, concerned that eliminating Athens would leave Thebes in a position to dominate central Greece. Rather than destroying Athens, Sparta preferred to preserve it as a counterweight to Thebes. Partners, once willing to accept Spartan leadership in order to defeat Athens, found Sparta’s actions after victory domineering. Persia, content to bankroll a destructive war among the Greek city-states, became concerned when it appeared Sparta would achieve a position of dominance.

Less than a decade after Sparta’s victory, Thebes and Corinth, in a stunning reversal, allied with Athens and obtained financial support from Persia to confront Sparta during the Corinthian War, 395-387 BCE. In this way, Persia was able to use Athens, Corinth, and Thebes to counterbalance Spartan power the way it had used Sparta, Thebes, and Corinth to balance against Athenian power during the Peloponnesian War.

Sparta’s situation deteriorated further. By 378 BCE, renewed tensions between Thebes exploded in another war. This time, Sparta was decisively defeated and reduced to the status of a second class power.


Thucydides offers many enduring insights for scholars and policymakers. New tensions emerge as great powers search for new allies and try to hold on to old ones. Once begun in earnest, great power competitions are likely to endure for decades, because of the resources great powers possess. Those resources make it highly likely conflict comes with an often terrible cost for the victor and for the vanquished.

Thucydides records that the Spartan king, Archidamus, “a man of intelligence and good sense,”[23] warned the assembled Spartans against underestimating the wealth of Athens and its readiness for war. He predicted that the Spartans would be leaving the costs of “this war to [their]children.”[24] If policymakers in the United States and China set themselves on a course of hostile conflict and confrontation, they must accept that this unstable and dangerous legacy is the one they too will likely leave their children.

Andrew Novo is Associate Professor of Strategic Studies at the National Defense University, Washington, D.C. With Jay Parker, he is the author of Restoring Thucydides: Testing Familiar Lessons and Deriving New Ones. The views expressed here are entirely his and do not reflect those of the National Defense University, the Department of Defense, or the United States government.

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Header Image: Thucydides (Hillsdale College)


[1] C. Todd Lopez, “Great Power Competition’s Resurgence,” March 21, 2019,

[2] Thucydides, The Peloponnesian War, trans. Martin Hammond, (Oxford: Oxford University Press, 2009), I.22.

[3] Polybius, The History, trans. Ian Scott-Kilvert, (London: Penguin, 1979), III.31.

[4] Thucydides, The Peloponnesian War, I.36.

[5] Thucydides, The Peloponnesian War, I.71.

[6] Thucydides, The Peloponnesian War, I.23.

[7] Thucydides, The Peloponnesian War, I.23.

[8] Graham Allison, Destined for War: Can America and China Escape Thucydides’s Trap? (New York: Houghton Mifflin Harcourt, 2017), p.vii.

[9] Thucydides, The Peloponnesian War, I.88.

[10] Thucydides, The Peloponnesian War, I.71-72.

[11] Novo and Parker, Restoring Thucydides, p. 73-97.

[12] Stephen G. Brooks and William C. Wohlforth, America Abroad: Why the Sole Superpower Should Not Pull Back from the World, (Oxford: Oxford University Press, 2018).

[13] U.S. Bureau of Economic Analysis. “Gross Domestic Product, Fourth Quarter and Year 2019,”,table%201%20and%20table%203).

[14] U.S. Census. “Trade in Goods with World, Seasonally Adjusted,”; “U.S. National Debt,”; “Key Figures Behind America’s Consumer Debt,”,credit%20cards%20and%20student%20loans.

[15] "World Economic Outlook Database, April 2020". International Monetary Fund.

[16] Agne Blazyte. “Merchandise trade balance in China from 2009 to 2019,”'s%20merchandise%20trade,nearly%20594%20billion%20U.S.%20dollars

[17] Probably typhus.

[18] Thucydides, The Peloponnesian War, V.14.

[19] Aristotle, The Athenian Constitution, Trans. H. Rackman (Cambridge: Harvard University Press, 1952), XXIV.1.

[20] Thucydides, The Peloponnesian War, II.7.



[23] Thucydides, The Peloponnesian War, I.79.

[24] Thucydides, The Peloponnesian War, I.81


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