We have already traced the steps by which the various cities composing the Confederacy of Delos gradually became subjects and tributaries of Athens. After this great change was effected, the only members of the original league who retained their independence were the wealthy and powerful communities of Chios and Lesbos. These two islands were allowed to retain undisturbed control of their own affairs, with the sole obligation of sending a fixed quota of ships to serve in the Athenian Navy. It does not appear that the performance of this duty was felt as a grievance, and no act of oppression had been committed by Athens, such as might have provoked her allies in Lesbos or Chios to turn against her. In both islands the general body of the citizens were on the whole friendly to the Athenians, who afforded them an effectual means of protection against the tyranny of the nobles, by summoning high-born offenders to be tried before the Athenian tribunals. [Footnote: The evidence for this statement will be found in Thucydides, viii. 48.] It was therefore not among the people at large, but among the privileged few, that any movement of revolt against Athens was to be expected. Some years before the outbreak of the Peloponnesian War the Lesbian malcontents had solicited the Spartans to help them in throwing off the yoke of Athens. This application, which was probably made at the time of the revolt of Samos, found no favour with Sparta, and nothing further was attempted on that occasion. But in the fourth year of the war alarming rumours were brought to Athens from Tenedos, a small island included in the Athenian alliance, whose inhabitants were jealous of the threatened ascendancy of Lesbos in the eastern districts of the Aegaean. There was a design, it was said, among the leading citizens of Mytilene, the principal city of Lesbos, to unite the inhabitants of the island by force under their rule, and renounce their allegiance to Athens. Help was expected from Sparta, and the Boeotians, who were of the same race as the Lesbians, were also in the plot. This statement was confirmed by envoys from Methymna, the second city of Lesbos, which stood apart from the conspiracy, and by certain citizens of Mytilene, who had turned informers from motives of private revenge.