DURING the fourth year of the war the Peloponnesians, under Archidamus, again repeated their invasion and ravage of Attica, which had been intermitted during the year preceding. As before, they met with no serious resistance. Entering the country about the beginning of May, they continued the process of devastation until their provisions were exhausted. To this damage the Athenians had probably now accustomed themselves: but they speedily received, even while the invaders were in their country, intelligence of an event far more embarrassing and formidable - the revolt of Mitylênê and of the greater part of Lesbos.
This revolt, indeed, did not come even upon the Athenians wholly unawares. Yet the idea of it was of longer standing than they suspected, for the Mitylenæan oligarchy had projected it before the war and had made secret application to Sparta for aid, but without success. Some time after hostilities broke out, they resumed the design, which was warmly promoted by the Bœotians, kinsmen of the Lesbians in Æolic lineage and dialect. The Mitylenæan leaders appear to have finally determined on revolt during the preceding autumn or winter. But they thought it prudent to make ample preparations before they declared themselves openly; and moreover they took measures for constraining three other towns in Lesbos - Antissa, Eresus, and Pyrrha - to share their fortunes, to merge their own separate governments, and to become incorporated with Mitylênê. Methymna, the second town in Lesbos, situated on the north of the island, was decidedly opposed to them and attached to Athens.
Though the oligarchical character of their government gave them much means of secrecy, still, measures of such importance could not be taken without provoking attention. Intimation was sent to the Athenians by various Mitylenæan citizens. Not less communicative were the islanders of Tenedos, animated by ancient neighbourly jealousy towards Mitylênê.