B.C. 408. The year following is the year in which the temple of Athena, in Phocaea, was struck by lightning and set on fire.17 With the cessation of winter, in early spring, the Athenians set sail with the whole of their force to Proconnesus, and thence advanced upon Chalcedon and Byzantium, encamping near the former town. The men of Chalcedon, aware of their approach, had taken the precaution to deposit all their pillageable property with their neighbours, the Bithynian Thracians; whereupon Alcibiades put himself at the head of a small body of heavy infantry with the cavalry, and giving orders to the fleet to follow along the coast, marched against the Bithynians and demanded back the property of the Chalcedonians, threatening them with war in case of refusal. The Bithynians delivered up the property. Returning to camp, not only thus enriched, but with the further satisfaction of having secured pledges of good behaviour from the Bithynians, Alcibiades set to work with the whole of his troops to draw lines of circumvallation round Chalcedon from sea to sea, so as to include as much of the river as possible within his wall, which was made of timber. Thereupon the Lacedaemonian governor, Hippocrates, let his troops out of the city and offered battle, and the Athenians, on their side, drew up their forces opposite to receive him; while Pharnabazus, from without the lines of circumvallation, was still advancing with his army and large bodies of horse. Hippocrates and Thrasylus engaged each other with their heavy infantry for a long while, until Alcibiades, with a detachment of infantry and the cavalry, intervened. Presently Hippocrates fell, and the troops under him fled into the city; at the same instant Pharnabazus, unable to effect a junction with the Lacedaemonian leader, owing to the circumscribed nature of the ground and the close proximity of the river to the enemy’s lines, retired to the Heracleium,18 belonging to the Chalcedonians, where his camp lay. After this success Alcibiades set off to the Hellespont and the Chersonese to raise money, and the remaining generals came to terms with Pharnabazus in respect of Chalcedon; according to these, the Persian satrap agreed to pay the Athenians twenty talents19 in behalf of the town, and to grant their ambassadors a safe conduct up country to the king. It was further stipulated by mutual consent and under oaths provided, that the Chalcedonians should continue the payment of their customary tribute to Athens, being also bound to discharge all outstanding debts. The Athenians, on their side, were bound to desist from all hostilities until the return of their ambassadors from the king. These oaths were not witnessed by Alcibiades, who was now in the neighbourhood of Selybria. Having taken that place, he presently appeared before the walls of Byzantium at the head of the men of Chersonese, who came out with their whole force; he was aided further by troops from Thrace and more than three hundred horse. Accordingly Pharnabazus, insisting that he too must take the oath, decided to remain in Chalcedon, and to await his arrival from Byzantium. Alcibiades came, but was not prepared to bind himself by any oaths, unless Pharnabazus would, on his side, take oaths to himself. After this, oaths were exchanged between them by proxy. Alcibiades took them at Chrysopolis in the presence of two representatives sent by Pharnabazus — namely, Mitrobates and Arnapes. Pharnabazus took them at Chalcedon in the presence of Euryptolemus and Diotimus, who represented Alcibiades. Both parties bound themselves not only by the general oath, but also interchanged personal pledges of good faith.

This done, Pharnabazus left Chalcedon at once, with injunctions that those who were going up to the king as ambassadors should meet him at Cyzicus. The representatives of Athens were Dorotheus, Philodices, Theogenes, Euryptolemus, and Mantitheus; with them were two Argives, Cleostratus and Pyrrholochus. An embassy of the Lacedaemonians was also about to make the journey. This consisted of Pasippidas and his fellows, with whom were Hermocrates, now an exile from Syracuse, and his brother Proxenus. So Pharnabazus put himself at their head. Meanwhile the Athenians prosecuted the siege of Byzantium; lines of circumvallation were drawn; and they diversified the blockade by sharpshooting at long range and occasional assaults upon the walls. Inside the city lay Clearchus, the Lacedaemonian governor, and a body of Perioci with a small detachment of Neodamodes.20 There was also a body of Megarians under their general Helixus, a Megarian, and another body of Boeotians, with their general Coeratadas. The Athenians, finding presently that they could effect nothing by force, worked upon some of the inhabitants to betray the place. Clearchus, meanwhile, never dreaming that any one would be capable of such an act, had crossed over to the opposite coast to visit Pharnabazus; he had left everything in perfect order, entrusting the government of the city to Coeratadas and Helixus. His mission was to obtain pay for the soldiers from the Persian satrap, and to collect vessels from various quarters. Some were already in the Hellespont, where they had been left as guardships by Pasippidas, or else at Antandrus. Others formed the fleet which Agesandridas, who had formerly served as a marine21 under Mindarus, now commanded on the Thracian coast. Others Clearchus purposed to have built, and with the whole united squadron to so injure the allies of the Athenians as to draw off the besieging army from Byzantium. But no sooner was he fairly gone than those who were minded to betray the city set to work. Their names were Cydon, Ariston, Anaxicrates, Lycurgus, and Anaxilaus. The last-named was afterwards impeached for treachery in Lacedaemon on the capital charge, and acquitted on the plea that, to begin with, he was not a Lacedaemonian, but a Byzantine, and, so far from having betrayed the city, he had saved it, when he saw women and children perishing of starvation; for Clearchus had given away all the corn in the city to the Lacedaemonian soldiers. It was for these reasons, as Anaxilaus himself admitted, he had introduced the enemy, and not for the sake of money, nor out of hatred to Lacedaemon.

As soon as everything was ready, these people opened the gates leading to the Thracian Square, as it is called, and admitted the Athenian troops with Alcibiades at their head. Helixus and Coeratadas, in complete ignorance of the plot, hastened to the Agora with the whole of the garrison, ready to confront the danger; but finding the enemy in occupation, they had nothing for it but to give themselves up. They were sent off as prisoners to Athens, where Coeratadas, in the midst of the crowd and confusion of debarkation at Piraeus, gave his guards the slip, and made his way in safety to Decelia.