How Thucydides still speaks to us, 2,500 years on

Power rarely collapses from weakness. It collapses from the consequences of misjudgement. The confrontation between the US and Israel with Iran may prove to be one of those moments. 

My late professor David L Larson of the University of New Hampshire, used to say that there is nothing ancient about the ancients. They are not relics of the past, but analysts of the present. He was absolutely right. 

Thucydides did not write history as narrative, but as analysis. He described not only what happened, but why states behave as they do when they believe themselves all-powerful. His History of the Peloponnesian War is not just about Athens and Sparta. It is about human nature under conditions of power, and the decisions that flow from it when judgement falters. That is why he still speaks to us, 2,500 years on. 

Thucydides observed something both simple and unsettling. States go to war not only out of perceived necessity, but because they believe they will prevail. Power alters perception. It compresses risk. It magnifies confidence. It creates a sense of inevitability and of control.  

Thucydides distilled this logic into a triad that endures: fear, honour and interest. Fear drives pre-emption. Honour drives escalation. Interest provides justification. Together, they form the grammar of conflict. 

At its height, Athens possessed naval dominance, economic strength, strategic confidence. Yet it embarked on the Sicilian expedition not out of necessity, but out of choice and belief that it would prevail. It believed in its superiority, in its control of events, and that its power would carry the day. It did not. The result was not simply defeat, but strategic collapse. The failure was not capability. It was judgement. 

Thucydides admired Pericles for good reason. Pericles understood limits. He aligned ends with means. He resisted impulse. He imposed discipline on power. After his death, that discipline eroded. Strategy gave way to rhetoric. Prudence yielded to ambition. Decision-making became reactive, shaped by internal pressures rather than coherent design. The disastrous Sicilian expedition followed. 

This is not an ancient story. It is our present. Power, without restraint, becomes erratic. Erratic power becomes dangerous to others and to itself.  

Thucydides also understood that power is not only material. It is perceived. States respond not only to power as it is, but to what they believe it will do. This is where statecraft falters. Unpredictability is mistaken for strategy. Signals are issued, revised, reversed. Positions shift. Commitments blur. Credibility erodes quietly.  

Deterrence weakens not because power disappears, but because its use becomes uncertain. When signals lose coherence, the strategic environment destabilises. 

Long before Thucydides, Greek myth captured a parallel truth. The golden apple of Eris – the goddess of discord – did not cause the Trojan War. It set in motion a chain of choices that revealed rivalries already present. Myth captures how conflict begins. Thucydides explains how it unfolds. This pattern – underlying tension, triggering event, and escalatory decision – is not confined to any one leader or moment. It is inherent in the exercise of power. 

What appears sudden is rarely so. It is the activation of tensions long in the making. In the current confrontation with Iran, the risk lies precisely here – not only in the balance or asymmetry of power, but in the triggers that convert tension into escalation. Power determines capacity.  

Triggers determine action. This dynamic is not unique to Iran. It applies wherever power meets perception under pressure. 

Thucydides understood how domestic dynamics shape external outcomes. Athens was not driven by strategy alone, but by debate, rivalry, persuasion. Leaders rose by appealing to the moment, not by sustaining long-term design. The result was escalation without coherence. 

This pattern endures. When foreign policy is driven by domestic politics, consistency erodes. Decisions accelerate. Risks are discounted. Outcomes become harder to control. The line between governance and demagoguery narrows.  

The most enduring insight is also the most dangerous. Power does not remove constraints. It obscures them. 

In the didactic Melian Dialogue, Athenians articulated a brutal realism: the strong do what they can, the weak suffer what they must. Yet even this clarity contained an illusion: that strength itself was sufficient. It was not. 

Power that overreaches invites resistance. Power that ignores limits creates new ones. Power that assumes itself unconstrained eventually meets constraint in its harshest form: failure. 

Today’s international system shows signs of rupture. The language of rules persists, but application is increasingly selective. Power is asserted more openly. Restraint is less evident.  

As Thucydides observed in his account of civil strife, “words had to change their ordinary meaning” to suit the moment. Reckless audacity became “courage”; moderation “cowardice”; prudence “weakness”. The insight resonates today. Language becomes an instrument of power – shaping perception, justifying action, and obscuring reality. In such an environment, Thucydides is not a historian of the past. He is an analyst of the present. 

His warning is not philosophical. It is practical. Power must be disciplined. It must be intelligible. It must be anchored in strategy, not impulse. Otherwise, it defeats its own purpose and produces the instability it seeks to manage. Worse, it leads to defeat.  

We are not witnessing the return of ancient Greece. But we are witnessing the persistence of human nature under conditions of power. This is what makes Thucydides diachronic – a historian for all ages. As he himself wrote, “my work is composed as a possession for all time, rather than a piece to be heard for the moment.” («κτῆμά τε ἐς αἰεὶ μᾶλλον ἢ ἀγώνισμα ἐς τὸ παραχρῆμα ἀκούειν ξυγκεῖται»). 

The question is not whether leaders possess power. It is whether they understand what power does: to judgement; to perception; to decision; and to human consequence. Power determines what states can do. But a single spark – misread, mishandled – often determines what they will do. That is the diachronic warning of Thucydides.