At that time the siege of Chalkedôn was being carried on by Thrasyllos, who had nearly succeeded in carrying a palisade round the city on its land side. This wall was now nearly completed. Placed almost immediately opposite Byzantion and thus forming a firm base of operations whenever he should attack that most important city, Chalkedôn, which had lately thrown off its dependency on Athens, was strenuously defended by the Spartans. While Thrasyllos was pushing on his works the Spartan garrison made a sortie from the town, and Pharnabazos, co-operating with them, made a simultaneous dash upon the besieging force with all his army. At that critical moment Alkibiades arrived in time to prevent the destruction of the Athenians thus caught between the Spartans in front of them and the Persians at their back. With his new Thrakian cavalry he charged Pharnabazos with such effect that the gallant Persian fled discomforted. He then led his troop round against the Spartans, who retired behind the walls of Chalkedôn, leaving a large part of their numbers behind them dead upon the field, including their commander, Hippokrates.
Having finished the wall of palisades by which the town was completely cut off from the land, he recrossed the Bosporos, with such troops as could be spared from the siege of Chalkedôn, to raise contributions for the war. At Selymbria, a Greek town on the Thrakian coast of the Propontis, he was called upon once more to prove his fearless intrepidity, his calmness and resource in the midst of danger, and his gentleness in the hour of victory. He arrived before the town with a body of his own hoplites and his Thrakian horsemen. Some of the citizens were willing to ally themselves with Athens, or rather, perhaps, were unwilling to struggle against one who seemed to be invincible. They agreed to open the gates to him at midnight, and promised to display a lighted torch upon the walls as a signal that they were ready to receive him. One of them betrayed the design to the authorities of Selymbria. The others, fearing the vengeance of the citizens, showed the signal from the walls an hour before the appointed time, and opened the city gates. Alkibiades, who had given orders for the main body of his men to be ready to enter the town with him at midnight, on seeing the signal, though his men were not yet ready, rushed to the open gate, followed by only thirty of his guard. He was joined by twenty of those who were friendly to him within the town. With this handful of followers he found himself in the narrow streets and in the midst of an angry multitude. Here again he was in imminent peril of his life. He refused to retreat, although he could not hope that thirty men, however brave, assisted by only twenty citizens, could hold their ground until his hoplites and his Thrakians should come to his aid. He ordered a trumpet to be sounded, and as calmly as if he was at the head of a victorious army, he made a proclamation ‘that the Selymbrians would incur the anger of the state of Athens if they dared to take up arms against the Athenians.’ His extraordinary coolness so frightened the people, who supposed a proclamation such as this would never have been made unless the whole army was behind him and entering the city, that they asked for conditions. While these were being arranged the rest of his army entered.
Selymbria was now at his mercy. According to the rights or wrongs of war, he might have robbed it of its riches and allowed the outrage of its citizens. He forbade both, and risked the anger of his half-tamed Thrakians, who could not understand how a hostile city could be taken without the necessary consequence of rapine, by sending them out of Selymbria baulked of their prey. Taking only a reasonable sum of money by way of tribute, he left a garrison behind to protect Selymbria from the Spartans.
The feeling of discontent with the policy of supporting Sparta against such an opponent now reached its height in the mind of Pharnabazos. He opened communications with Thrasyllos, who had been left to carry on the siege of Chalkedôn while Alkibiades was away strengthening the power of Athens on the Propontis, and collecting tribute for the support of her defenders. He promised an immediate payment of twenty talents, proposed a treaty of peace, and offered an escort and safe-conduct to an Athenian embassy, which he suggested should be sent to the Great King to settle the terms upon which a final peace might be made between Persia and Athens.
In the meantime a truce was to be made between the satrap and Alkibiades. The satrap’s terms were accepted and the embassy was sent. It included one whose travels and troubles we have already spoken about—the unfortunate Mantitheos, whose sufferings were now to be continued for three years to come. But Pharnabazos was not content with the word or oath of a subordinate before he withdrew his troops finally from the support of the Spartans. He insisted that the general-in-chief must himself attest his consent to all the terms of the treaty. Alkibiades confirming them by his own solemn oath, the satrap made mutual covenants of friendship, alliance, and hospitality with him, treating him throughout more as an autocratic sovereign than as a general-in-chief of a republic.
Having fortified Chrysopolis, the port of Chalkedôn, by building a strong tower which looked across the narrow strait to Byzantion, Alkibiades now set about his long-meditated siege of that important place which was the bulwark of the Bosporus and the key to the Euxine trade. But Byzantion was strongly guarded by stone walls without and by an unrelenting warrior within, the iron-willed and iron-hearted Klearchos, whom Sparta had sent as her best commander to hold a place of such inestimable value. He was supported by a strong body of his trained citizens and sturdy Boiotians. The Athenian fleet blockaded the port and every entrance by sea; the Athenian army gradually drew round it on the land side, and stopped all help from coming to the famine-stricken people of that great city. Klearchos closely hoarded the food he had stored up within. ‘This,’ he said, ‘is wanted by those who can bear arms and fight; the rest, if needs be, can starve.’
There was no sign of surrender, and the summer passed away. Overtures were at length made to the Athenian general by some of the principal inhabitants. They told him they had no love for their defenders, that they detested the Spartan general, who had left them in their dire want to go to seek aid from Pharnabazos. They agreed to open the Thrakian gate to the besiegers. Alkibiades knew how much blood must be wasted on the assault of such a place. No commander was ever more careful of the lives of men committed to his trust than he. In the whole of his career there is no instance of any reckless sacrifice of life in order to gain even the most important conquest, nor of any cruelty done, or permitted to be done, on those whom the fortune of war delivered over to his power.
If it was possible to get possession of the coveted city in any other way, he determined to avoid the carnage on both sides, which must inevitably happen if a place so strongly fortified was stormed. As clever in stratagem as he was fearless in fight, he made a pretence of retiring from the siege and carrying his troops away. He ordered the triremes to row off into the Bosporos, as though he was abandoning a hopeless task. Then, at midnight, some of the ships returned, and the sailors, landing with great clamour, attacked the eastern gate. The Spartan troops rushed to that spot and forced the few Athenian sailors who had landed to retreat to their ships. At that moment the Thrakian gate was opened by friends within, and Alkibiades, at the head of his hoplites, who had silently returned in the darkness of the night, entered Byzantion.
The Spartans and their allies discovered the trick that had been played upon them, and hastily came back to meet the enemy, who were now in the centre of the city. But, posted in strong positions in the main streets and squares, the Athenians made havoc of both Boiotians and Spartans, and the Byzantine soldiers turned upon those whom the people had good reason to look upon rather as oppressors than protectors. The Spartans fought with the courage of despair, but they were all slain at length, except some five hundred, who surrendered. The inhabitants were well treated, although they had revolted from Athens when she was in her greatest need. They again accepted her mild sovereignty, and agreed to pay the usual tribute.
Now, with Chalkedôn in his power, Chrysopolis in his hands, and Byzantion garrisoned by Athens, Alkibiades placed the Euxine Sea in her control once more. What that meant at such a time can only be understood when one recollects the extensive trade of the great inland sea and the low state to which Athens of late had been reduced. It drove her enemies out of these waters, and it gave her whatever dues she chose to impose on all the rich merchant ships passing to and fro with their cargoes of slaves, of skins, of fish, and, what to Athens was more than all, their loads of corn from the Euxine shores. For she had been deprived of the produce of her own lands ever since King Agis and the Spartans had Dekeleia in their possession, and since the defection of Euboia, her other granary, she had to look to the Euxine to supply her with the bare necessities of life. This was now thrown open to her.