The study of Thucydides has become so sophisticated that it has reached the point of overcorrection. When it comes to reading and interpreting the Athenian admiral, exile and historian, who wrote of the cataclysmic Peloponnesian war (431-404BC) between Athens, Sparta and their allies, specialist scholars frequently accuse International Relations theorists of oversimplification. They particularly chide realists—those who see international relations as anarchic, inherently war-prone and competitive—for claiming Thucydides as their intellectual ancestor. When realists try to tease out general patterns from Thucydides that guide our understanding of human behaviour, they attract eye-rolling frustration. Graham Allison was most recently met with scorn when he applied Thucydidean insight into the US-China antagonism, identifying a pattern of power-transition crisis echoing the power-shift that Thucydides said was the ‘truest cause’ of war between Athens and Sparta.

But this is not particular to Allison. For some critics, the whole endeavour to pull from history a picture of recurring structural pressures that can lead to war, or to hold up examples from antiquity to guide the present, is suspect  and dangerously deterministic. Some even argue that International Relations scholars should de-centre Thucydides’ history, one of the greatest works on conflict and struggle in the western tradition, stop treating it as a forerunner of their theories, or even, just stop reading it altogether. In this way, complexification can lead to its own reductionism, having the effect of turning Thucydides’ history into little more than a parochial anecdote.

Indeed, Thucydides’ work is a layered and sometimes ambiguous work that modern scholarship has superbly excavated. For many lively minds, our main duty is to read it with caution, to resist generalisation, and by appealing to context, to find subtle meaning between the lines. But in the effort to correct superficial readings, to uncover the text’s rich complexity, interpreters can over strive, inadvertently diluting its core insights. For the main duty of academic minds is not just to uncover nuance, but also to find fundamentals and larger patterns. If we lose sight of this, we can nuance a text to death. Nuance, indeed, can be over-rated. For all the caveats, Thucydides was still a realist.

What does it mean to say Thucydides was a realist? It is to say that he was one of the founders of a pessimistic intellectual tradition that believes the world, like the one he endured, is inherently a cold, harsh, dangerous place in which power and its acquisition is paramount. In this world, interests diverge and clash, and cooperation is bound to be impermanent. There is no reliable authority above the fray. No-one can be certain of others’ intentions, which can change. This makes for a world of ultimate solitude. Ruthless self-help and prudent self-restraint are both imperative. To survive in it, polities must accept and work within its constraints.

Thucydides’ history is also many other things. It is part investigative and part didactic. It dwells on suffering, greatness, chance, honour, pity, the dangers of demagoguery, and the author’s own ambition for intellectual immortality. Thucydides recast Athens’ defeat as a tragedy, too, and propagandised for his own political faction. As an exile and a patriot, he mixed horror in Athens’ descent into tyranny with pride in its power.

Still, the work also builds on a core worldview, a set of assumptions about what drives humans and undoes them. In the best ‘realist’ reading of Thucydides’ history, to be prudent in realist terms means looking first to your ramparts and maintaining robust defences, being wary of over-reliance on international friendships, notions of justice, or appeals to heaven, or to a harmony of interests, and remembering that hard power unapologetically applied is the ultima ratio. More agonisingly, it means that while states should be continuously prepared for war, they should also be mindful that unleashed, war can destroy everything.

Thucydides wrote in the belief that we can devise large-scale maps about how the world works, what we call ‘theory.’ As a universalist, he offered empirical observations about the patterns of international politics that hold across time and space. Assuming the past can shed light on the future given the constants in human nature, he wanted it ‘to be judged useful by those who want to understand clearly the events that happened in our past’ which would ‘at some time or other and in much the same ways, be repeated in the future.’ In this spirit, consider some propositions that we can derive from the text.

In a hostile world, fear above all defines the human condition.

Fear haunts and overshadows Thucydides’ history more than any other thing. The word for ‘danger’ occurs over two hundred times. After all, as the scholar Arthur Eckstein observes, the physical destruction of city-states was frequent enough to insure against. In more than forty cases in the classical period, the poleis suffered this calamity. And if not the destruction of the city, defeat could mean the destruction of city walls and the curtailing of independence. Leading up to the Peloponnesian war, Athens and Sparta had acquired their capabilities only through a ‘hard school of danger.’ Danger, ill-prepared for or mishandled, could mean the destruction of one’s world. Earlier generations in his telling faced ‘constant pressure’ and were either constantly taking flight or had to put up with being dominated by the strong. External dangers bear down, sooner or later, on all polities, while human responses to danger if governed by reckless urges can then make the world even deadlier. Sparta fears the future, given Athens’ growth as a tributary empire and naval heavyweight, and those who carry the day in its internal debate adopt a preventive logic, better to strike now than later against a strengthening enemy, or risk losing their allies. At the same time, another fear persists, that ruin can come from within. As the Spartan king says, ‘I fear more our errors than the enemy’s designs.’ Anticipating the idea of what we now call ‘anarchy’, the absence of a supreme supranational authority that keeps the peace, trusting behaviour that is honourable in private life is ill-advised abroad.

And in Thucydides’ account, fear, in a controlled and rational form, is warranted. A state of fearlessness — thinking one is secluded or separate from danger — can be fatal. In a world of predation, no state is exempt or special, no matter their ancestry or geography. When Thucydides narrates the Thracian massacre of the small city Mycalessus, he notes that the assault succeeded because ‘the inhabitants were caught off their guard, since they never expected that anyone would come so far from the sea to attack them. Their wall, too, was weak and in some places had collapsed…and the gates were open, since they had no fear of being attacked.’ This same insight, the warning against delusional insularity, Thucydides extended to Athens itself. The death of its elite guardian Pericles helped loosen its sense of restraint, and a growing belief, bloated by success, that it is exceptional, abandoning any self-doubt.

Power, not law, morality or norms is the most important force.

Power is the main currency in Thucydides’ history, its gain and loss the chief political concern. In this respect, Thucydides was a direct ancestor to modern realism and articulated the regard for what Robert Gilpin called ‘the primacy in all political life of power and security in human motivation.’ Pericles’ famous funeral speech of Athenian self-celebration dwells most on Athens’ power, the asset that makes and protects all else. The need to acquire power to ward off danger tends to trump other impulses. That is the necessity, or constraint that conditions (though does not determine) behaviour. All allies fighting on both sides in Syracuse were there, he tells us, because of the pressure of various necessities, more than other cultural fidelities or principles. ‘They stood together not because of any moral principle or ethnic connection; it was rather because of the various circumstances of interest or of compulsion in each particular case.’

But in a tragic world, while states should pursue power to be secure, successfully doing so can also destroy them. Long wars especially rot a country politically, loosen its restraint and corrupt its politics. Tragically, success can give polities stupid ideas about being transcendent, and wrecks them through disastrous peripheral wars or actions that cause self-encirclement. Thus, there is a tension in Thucydides’ vision. The tension is not only between the need for both power and restraint, mindful prudence with determined action. It is also between structure and agency. Necessity constrains but does not dictate behaviour. There is still agency, hence Thucydides’ effort to re-construct the turbulent debates that led to final decisions. But the unforgiving world of self-help, what we now call the anarchic international system, tends to punish imprudence.

This brings us to the most contentious issue: the clash of power and justice, strength and morality, as articulated in the famous Melian Dialogue. Recall that in 416 BC, Athens with its naval supremacy demanded the allegiance of a polity that was formally neutral, Melos, and massacred and enslaved the small island population when it refused. In Thucydides’ set-piece exchange, whereas the Melians in defiance place their hopes in the gods, in their kindred Spartan allies, and in appeals to justice, a swaggering Athens speaks in the stark language of power. With undisguised clarity, the Athenians insist that the dominance of the strong and the urge to rule prevails. This foreshadows Athens’ own later fate, praying fruitlessly to the gods for salvation after their disastrous expedition to Sicily.

For humanistic readers of Thucydides, it is the Melians’ message that most reflects the author’s mind. They read the episode as an indictment of Athens’ debasement, its descent from being the moral leader of the pan-Hellenic world into a murderous, militarised arrogance, a new version of Achaemenid Persia’s despotism. For them, Thucydides’ history serves primarily as a cautionary fable against imperial aggrandizement and the hubris of power, despite Thucydides’ ally Pericles being a man of empire. Written often with the self-defeating excesses of Vietnam and Cambodia in mind, their Thucydides becomes a prototype of the liberal conscience and its stress on international law and norms.

This version captures part of the truth. But given the text and history as a whole, it is likelier that different parts of Thucydides’ worldview are reflected in both the words of the Melians and the Athenians. Given what happened to the Melians, and Thucydides’ emphasis elsewhere on the harsh realities of power, he was surely also suggesting something about the costs of placing trust in higher authorities or principles, and the fragility of law under the brutalising pressures of conflict. The Melians have an ‘expensive’ hope, a noble one, perhaps, but ruinously costly all the same. As Fouad Ajami noted of the Melians, in his rebuttal to Samuel Huntington’s forecast that civilisational ties will determine allegiances, ‘Besieged by Athens, they held out and were sure that the Lacedaemonians were “bound, if only for very shame, to come to the aid of their kindred.” The Melians never wavered in their confidence in their “civilizational” allies: “Our common blood insures our fidelity.” We know what became of the Melians. Their allies did not turn up, their island was sacked, their world laid to waste.’

If there is connecting tissue between this atrocity and Athens’ subsequent fall, it lies less in Athens’ inhumanity, and more in the punishment a debased Athens attracted by squandering its power materially in a failed military expedition, out of a sense of fearless exceptionalism. Athens fell not primarily because it was indecent or mistreated allies or subjects, but because it had become disastrously fearless. For the most part, immoral behaviour was reprehensible in itself, not because morality determined the war’s outcome. The very notion that overreaching hubris leads to downfall implicitly relies upon a wider world inhabited at least partly by other merciless states, willing and ready to abandon or to pounce.

True, in his depiction of the bloody Corcyrean revolution, Thucydidean speaks of ‘common laws of humanity’ that the vengeful should observe, since they will need it later.  But Victorious Sparta and its allies also committed atrocities that Thucydides chronicled. Note, for instance, the massacres in Lecythus and Hysiae; the doomed appeal of the Plataeans to the Spartans; Syracuse’ slaughter of Athenian soldiers on the banks of the Assinarus river; supported coups by murderous oligarchs; or the secret slaughter of two thousand helots through a false promise of freedom, by a Sparta preoccupied with ‘security.’ And in Thucydides, it is most often power shifts that trigger the revolt of tributary allies.

The reckless invasion of Sicily was one of the transforming events, not maltreatment of the weak, that then helped entice an onlooking Persian superpower to intervene on Sparta’s side and tip the scales. Darius II injected gold and troops into the contest to weaken Athenian power and reconquer the Ionian Greeks, but not because he was affronted by Athenian atrocities. To the limited extent that Thucydides depicts Persia’s intervention, he portrays pragmatic, hard-headed satraps, men of cold calculation who want a return on their investment. On the whole, in his telling, this was not a contest for hearts and minds through adherence to norms. Thucydides may not have been simply the forerunner of Henry Kissinger or the enthusiasm for bloody, pitiless machtpolitik. But neither was he an early Gareth Evans, Australia’s former Foreign Minister and avowed liberal internationalist.

Thucydides’ work has sinew precisely because he depicts humans trying to be agents within the constraints of the world’s relentless pressure. He retains a capacity for pity while unsparingly depicting power’s brutal ways. He beholds and chronicles the suffering of others even as his work is pessimistic about the possibility of transforming an inherently insecure world. In the words of classical scholar Erich Gruen, ‘he recognized that men generally act in accordance with expediency and advantage. But it does not follow that he looked upon those acts with cold detachment.’

States should face realities without euphemism.

Realism at its core is the capacity to look at the world without euphemism. In that spirit, Thucydides is a tonic to wishful thinking, thereby supplying the intellectual tools to resist fanciful expectations. If there is one source of false hope in our time, leading to ill-preparedness and shock, it is the widespread conceit that the ‘twenty first century’ or ‘Europe’, or something in our contemporary condition, should rule out certain bad things happening.

As we too have discovered, ‘hope is an expensive commodity.’ Against earlier expectations that a growing China would supplicate itself to US hegemony, it grabs land, coerces and threatens far and wide, and has embarked on a vast naval and nuclear build-up. Against confident earlier claims that his regime ‘must’ go, Gulf states reconcile themselves to Syrian tyrant Bashar al-Assad’s victory after a civil war of unimaginable terror. And against prophecies that geopolitics is an illusion and that Russia would not dare go further than subversion around the edges, Vladimir Putin has launched his latest aggressive lunge into Ukraine. Events in Ukraine are catastrophic, yet the disbelief that they are happening suggests something of this problem. In post-war history, continental Europe was for long periods an armed pair of camps, at times the scene of brutal military suppression, from Berlin to Prague, the site of terrible bloodletting in the Balkans and an ongoing war in Ukraine since 2014. Yet the outcry in some quarters reflects an unexamined view of a tranquil region, destined by history or merit not to experience the current agony. People will disagree exactly how we got here. But the failure to take Russia seriously as a determined, risk-acceptant adversary, or to recognise that even liberal Europe could plunge into nuclear crisis, was long in the making.

In the face of hard realities, Thucydides embodied the dual concern of classical realism, consciousness of external threats while being wary of our capacity for self-destruction, to fall prey to irrational emotions and false hope. An age of blood and iron is well and truly now underway, and the bitter winds of economic warfare are only just beginning to blow back on us all. It is not a bad time, then, to think through what it means to be prudent, while avoiding excess brutality and the corruption of our polities. Thucydides’ realism, austere yet humane, should both shake and fortify us in the hard days ahead.