The destruction of the Sicilian armament was a fatal blow to the power of Athens. It is astonishing that she was able to protract the war so long with diminished strength and resources. Her situation inspired her enemies with new vigour; states hitherto neutral declared against her; her subject-allies prepared to throw off the yoke; even the Persian satraps and the court of Susa bestirred themselves against her. The first blow to her empire was struck by the wealthy and populous island of Chios. This again was the work of Alcibiades, the implacable enemy of his native land, at whose advice a Lacedaemonian fleet was sent to the assistance of the Chians. Their example was followed by all the other Athenian allies in Asia, with the exception of Samos, in which the democratical party gained the upper hand. In the midst of this general defection the Athenians did not give way to despair. Pericles had set apart a reserve of 1000 talents to meet the contingency of an actual invasion. This still remained untouched, and now by an unanimous vote the penalty of death, which forbad its appropriation to any other purpose, was abolished, and the fund applied in fitting out a fleet against Chios. Samos became the head-quarters of the fleet, and the base of their operations during the remainder of the war.

After a time the tide of success began to turn in favour of the Athenians. They recovered Lesbos and Clazomenae, defeated the Chians, and laid waste their territory. They also gained a victory over the Peloponnesians at Miletus; while the Peloponnesian fleet had lost the assistance of Tissaphernes, the Persian satrap, through the intrigues of Alcibiades. In the course of a few months Alcibiades had completely forfeited the confidence of the Lacedaemonians. The Spartan king Agis, whose wife he had seduced, was his personal enemy; and after the defeat of the Peloponnesians at Miletus, Agis denounced him as a traitor, and persuaded the new Ephors to send out instructions to put him to death. Of this, however, he was informed time enough to make his escape to Tissaphernes at Magnesia. Here he ingratiated himself into the confidence of the satrap, and persuaded him that it was not for the interest of Persia that either of the Grecian parties should be successful, but rather that they should wear each other out in their mutual struggles, when Persia would in the end succeed in expelling both. This advice was adopted by the satrap; and in order to carry it into execution, steps were taken to secure the inactivity of the Peloponnesian armament, which, if vigorously employed, was powerful enough to put a speedy end to the war. In order to secure his return to Athens, Alcibiades now endeavoured to persuade Tissaphernes that it was more for the Persian interest to conclude a league with Athens than with Sparta; but the only part of his advice which the satrap seems to have sincerely adopted was that of playing off one party against the other. About this, however, Alcibiades did not at all concern himself. It was enough for his views, which had merely the selfish aim of his own restoration to Athens, if he could make it appear that he possessed sufficient influence with Tissaphernes to procure his assistance for the Athenians. He therefore began to communicate with the Athenian generals at Samos, and held out the hope of a Persian alliance as the price of his restoration to his country. But as he both hated and feared the Athenian democracy, he coupled his offer with the condition that a revolution should be effected at Athens, and an oligarchy established. The Athenian generals greedily caught at the proposal; and though the great mass of the soldiery were violently opposed to it, they were silenced, if not satisfied, when told that Athens could be saved only by means of Persia. The oligarchical conspirators formed themselves into a confederacy, and Pisander was sent to Athens to lay the proposal before the Athenian assembly. It met, as it might be supposed, with the most determined opposition. The single but unanswerable reply of Pisander was, the necessities of the republic; and at length a reluctant vote for a change of constitution was extorted from the people. Pisander and ten others were despatched to treat with Alcibiades and Tissaphernes.

Upon their arrival in Ionia they informed Alcibiades that measures had been taken for establishing an oligarchical form of government at Athens, and required him to fulfil his part of the engagement by procuring the aid and alliance of Persia. But Alcibiades knew that he had undertaken what he could not perform, and he now resolved to escape from the dilemma by one of his habitual artifices. He received the Athenian deputation in the presence of Tissaphernes himself, and made such extravagant demands on behalf of the satrap that Pisander and his colleagues indignantly broke off the conference.

Notwithstanding the conduct of Alcibiades the oligarchical conspirators proceeded with the revolution at Athens, in which they had gone too far to recede. Pisander, with five of the envoys, returned to Athens to complete the work they had begun.