=168.= The Athenians, with their ally Sital´ces, a Thracian chief, were warring in the north with little success. Sitalces, with an irregular but powerful host of 150,000 Thracians, invaded Macedonia with the intention of dethroning Perdiccas. The Macedonians, unable to meet him in the open field, withdrew into their fortresses, and Sitalces, who had no means for conducting sieges, retired after thirty days. Phor´mio, an Athenian captain, gained two victories, meanwhile, in the Corinthian Gulf, over a vastly superior number of Spartans. In the first engagement he had but twenty ships, to the Spartan forty-seven; in the second, without reinforcements, he met a fresh Spartan fleet of seventy-seven sail. [Sidenote: B. C. 428.] The fourth year of the war was marked by the revolt of Mytilene, capital of Lesbos. Envoys were sent to Sparta to implore assistance, which was willingly granted, and the Mytilenians were received into the Peloponnesian League. =169.= In the spring of 427, the Spartan fleet advanced to Mytilene, but it arrived only to find the town in the possession of the Athenians. Nearly reduced by famine, the governor, by the advice of a Spartan envoy, had armed all the men of the lower classes for a last desperate sortie. The result was contrary to his expectations. The mass of the Mytilenian people preferred the Athenian supremacy to that of their own oligarchic government. Emboldened by their arms, they declared that they would treat directly with the Athenians, unless all their demands were granted. The governor had no choice but to open negotiations himself. The city was surrendered, and the fate of its inhabitants was left to be decided by the popular assembly in Athens, whither the ring-leaders of the revolt were sent. =170.= A thousand Athenians assembled in the Agora to decide the fate of their prisoners. Salæ´thus, the Spartan envoy, was instantly put to death. With regard to the rest, a spirited debate ensued. Cleon the tanner, the former opponent of Pericles, took a prominent part; and in spite of more humane and moderate counsels, actually succeeded in carrying his brutal proposition, to put to the sword all the men of Mytilene, and sell the women and children into slavery. Iniquitous as such an order would be in any case, it was the more so in this, because the greater number of the Mytilenians were friendly to Athens, while the revolt had been the act of the oligarchy, who were enemies of the people. So strong had been the opposition, that Cleon feared a reversal of the sentence, and therefore had a galley instantly dispatched to Lesbos, with orders for its immediate execution.