The Persian War was the greatest action of earlier times, yet that was 23 speedily settled in two battles at sea and two on land. But the present war lasted a long time and in the course of it Greece was afflicted with sufferings unprecedented in any comparable period of time. Never before were so many cities captured and laid waste – some by barbarians and others by Greeks fighting wars among themselves (and some of these cities went on to be resettled with new inhabitants after they had been captured).Never before were so many men made exiles, never before was there so much slaughter – some in the course of the war itself and some as a result of internal conflicts. And things that in the past were reported on the basis of hearsay, where the actual evidence was rather flimsy, now ceased to be incredible: earthquakes, which spread to most parts of the world and were also very violent; eclipses of the sun, which became more frequent than those in past memory; great droughts in some places, and arising from them both famines and the most damaging thing of all, which wiped out part of the population – the deadly plague. All these disasters descended on them at the same time along with this war.

The Athenians and Spartans began the war when they broke the thirty-year truce they made after the capture of Euboea. To explain why they broke it I first set out the reasons they gave and the matters of dispute between them so that no one in future ever need enquire how it came about that so great a war arose among the Greeks. I consider the truest cause, though the one least openly stated, to be this: the Athenians were becoming powerful and inspired fear in the Spartans and so forced them into war.

Summer [IV 1–49]

The following summer, at about the time the first ears of corn were showing, ten Syracusan and the same number of Locrian ships sailed to Messina in Sicily, where they had been invited in by the inhabitants, and took control of it. Messina now revolted from the Athenians. The chief motive the Syracusans had for doing this was that the place offered an entry point into Sicily and they were afraid that the Athenians might establish a base there for some later attack with a larger force. The Locrians for their part were motivated by their enmity with the Rhegians, whom they wanted to engage in war on two fronts, both by land and by sea. Indeed, the Locrians had at the same time mounted a full-scale invasion of Rhegian territory to stop the Rhegians going to help the Messinians; they were also responding to some Rhegian exiles who lived among the Locrians and had added their encouragement. The Rhegians had for a long while been in a state of internal conflict and it was not possible for them at that time to hold off the Locrians, who were consequently all the more eager to attack them. The Locrians wasted their land and then withdrew their infantry, while their ships continued to guard Messina. Meanwhile they were also manning other ships to be stationed at Messina and to continue the war from there.

At about the same time that spring, before the corn was fully ripe, the Peloponnesians and their allies invaded Attica, led by Agis, son of Archidamus and king of the Spartans. They encamped there and set about wasting the land.

Summer [V 52–55]

Right at the start of the following summer the Boeotians took over Heracleia, which had been badly damaged after the battle, and they dismissed the Spartan Agesippidas for his poor leadership. They took over the place, fearing that while the Spartans were distracted by their troubles in the Peloponnese the Athenians might seize it. The Spartans, however, were angry with them.

The same summer Alcibiades son of Cleinias, now one of the Athenian generals, acting in conjunction with the Argives and their allies, entered the Peloponnese with a small force of Athenian hoplites and archers along with allied troops he gathered from elsewhere. He travelled through the Peloponnese with this army, establishing the position of the alliance generally. He also persuaded the people of Patrae to extend their walls down to the sea and was intending himself to fortify Rhium in Achaea. However, the Corinthians and the Sicyonians and others who were directly threatened by such a fortification came and put a stop to it.

Summer [V 1–12]

The next summer the one-year treaty had come to an end after being extended to the time of the Pythian Games; and during the truce the Athenians relocated the Delians from Delos, in the belief that because of some ancient offence they had still been in a state of pollution when consecrated and that there had also been an omission in the act of purification, though they had thought they had followed the correct procedure in removing the graves of the dead, as I recounted earlier. The Delians set off and each made their own way to settle at Atramyttium in Asia, which Pharnaces had made available to them.

After the truce expired Cleon got the agreement of the Athenians and sailed to the Thracian region, taking with him 1,200 Athenian hoplites and 300 cavalry, plus a larger force of allied troops and thirty ships. He first put in at Scione, which was still under siege, and taking on some additional hoplites from the garrison there he sailed down to the Toronaean port of Cophus, which is not far from the city. From there, when he gathered from deserters that Brasidas was not in Torone and that those in the city were no match for his own force, he marched his infantry into the city and sent ten ships to sail round to the harbour. He first came to the surrounding wall that Brasidas had thrown around the city. Brasidas was wanting to include the suburb within it and after demolishing part of the old wall he had thus made one city of Torone.

Summer [V 25–35]

After the treaty and the alliance were made between the Spartans and the Athenians at the end of the ten-year war, in the ephorate of Pleistolas and the archonship of Alcaeus, there was peace among the parties that accepted these agreements; but the Corinthians and some of the cities in the Peloponnese tried to destabilise the arrangements, and that immediately led to further disturbance in the relations between Sparta and her allies. And as time passed the Spartans began to arouse the suspicions of the Athenians too, by not implementing some of the specific provisions from the agreements. For six years and ten months the two sides refrained from invading one another's territory, but elsewhere the truce failed to hold firm and they inflicted as much damage on each other as possible; and then they were finally driven to break the treaty concluded after the ten-year war and reverted again to open warfare.

The same Thucydides of Athens has written down these events too, setting them out in sequence by winters and summers, down to the time when the Spartans and their allies put an end to Athenian rule and captured the long walls and the Peiraeus. At that point the war had lasted a total of twenty-seven years. As for the agreement that intervened in the middle, one would be quite wrong to think that this period did not count as a state of war. For looked at carefully in the light of the relevant facts it will be seen that one cannot describe as ‘peace’ a situation in which the two sides neither restored nor received back everything that had been agreed by treaty; and quite apart from that, there were violations of the treaty on both sides in the Mantinean and Epidaurian conflicts among others, the allies in Thrace remained just as hostile to Athens, and the Boeotians were observing a truce which only lasted ten days at a time.

This synopsis is intended to give readers a schematic guide to the contents and to enable them to locate key events and phases of the action within the overall chronology. It should be remembered, however, that the conventional division of the text into books, chapters and sections was not one created by Thucydides himself but was imposed by later editors (see introduction, pp. 17–18). I have preserved it for ease of reference to the secondary literature and for cross-reference within the text itself, but I have made it structurally and typographically subordinate to the division by years and campaigning seasons, which Thucydides himself saw as his particular innovation in the arrangement of his history (see II 1, V 20 and note on calendar, pp. lviii–lix).

[BOOK I]

Thucydides is a foundational author in the history of political thought. He stands at the very start of reflective thinking about politics in the western tradition and that in itself gives his voice a great freshness, force and originality. But it also presents us with some immediate problems of understanding, since the sort of distinctions we now make between political science, political theory, political history and the study of international relations did not exist in his day, though he has on occasion been claimed as the originator of each of these modern ‘subjects’.

One key aim of this series is to present each author and text in their proper cultural and historical context and to avoid importing into our understanding of them anachronistic concepts derived from later developments and theories. I have tried to take this objective seriously in various ways. First, and perhaps controversially, I have not called the text by its traditional title, ‘The Peloponnesian War’, which is not a title we have any evidence Thucydides himself used and which was seen to be one-sided even in his own time. Secondly, in structuring the work I have given precedence to the internal divisions by years and campaigning seasons that Thucydides chose to employ rather than the conventional division into ‘books’, which was again a later addition (though I have retained the latter as background headings for ease of cross-reference within the text and to the secondary literature). These two tactics are intended to help prevent us projecting false assumptions on to the work even before we start reading it.

Thucydides is the author of one of the earliest and most influential works in the history of political thought. His subject was the conflict we now call the ‘Peloponnesian War’, the great war between Athens and Sparta and their respective allies, which lasted from 431 to 404 BC (with a break in the middle) and ended with the defeat of Athens and the dissolution of the Athenian empire. Thucydides saw this as a momentous and historic conflict, on an unprecedented scale, and he states his ambition of producing a full and objective account that will be ‘a possession for all time’. His book does indeed contain a very detailed record of the events of the war, which includes such famous set-pieces as Pericles’ Funeral Speech, the plague in Athens, the civil disorder in Corcyra, the debates on imperialism over Mytilene and Melos, and the disastrous failure of the Athenian expedition to Sicily. But through these narratives he also presents a sustained and sophisticated study of political power itself – its exercise and effects, its agents and victims, and the arguments through which it is justified and deployed.

This was a new kind of history – rationalistic in its purpose, self-conscious and explicit in its methodology – and Thucydides himself was very concerned to distinguish it from the work of his predecessors. But it would be anachronistic to classify his ‘history’ too narrowly. It was conceived in a fifth-century BC milieu of still emergent literary forms in drama, rhetoric, logic, physics and philosophy as well as in history (all these names of ‘subjects’ are derived from Greek words), and at a time when literacy was rare. Thucydides’ work draws on most of these other genres (as well as on the earlier model of Homer’s oral epic) and we do well to approach it free from the particular assumptions we bring to historical texts in our own culture.

Summer [V 84–115]

The next summer Alcibiades sailed to Argos with twenty ships and arrested those Argives who still seemed to be suspect figures and sympathisers of the Spartans. There were 300 of them in all and the Athenians deposited them on nearby islands that they controlled.

The Athenians also mounted an expedition against the island of Melos, with a force consisting of thirty ships of their own, six from Chios and two from Lesbos, together with 1,200 Athenian hoplites, 300 archers, 20 mounted archers and about 1,500 hoplites from their allies and the islanders. The Melians are Spartan colonists and were unwilling to recognise Athenian authority as the other islanders did. At first they stayed neutral and took no active part, but when the Athenians tried to force them by wasting their land they openly put themselves on a war footing. The Athenians therefore encamped in their territory with the forces mentioned above, but before doing any damage to the land the Athenian generals, Cleomedes son of Lycomedes and Teisias son of Teisimachus, sent envoys first to make proposals to the Melians. The Melians did not bring this delegation before the people in assembly but told them to explain the business they had come on to the authorities and the smaller ruling group. So the Athenian envoys addressed them as follows.