(M471) Pericles was thus the leading citizen of his country, when he advocated the junction of the Peireus with Athens by the long walls which have been alluded to, and when the Spartan army in Bœotia threatened to sustain the oligarchal party in the city. The Athenians, in view of this danger, took decisive measures. They took the field at once against their old allies, the Lacedæmonians. The unfortunate battle of Tanagra was decided in favor of the Spartans, chiefly through the desertion of the Thessalian horse. (M472) Cimon, though ostracised, appeared in the field of battle, and requested permission to fight in the ranks. Though the request was refused, he used all his influence with his friends to fight with bravery and fidelity to his country’s cause, which noble conduct allayed the existing jealousies, and through the influence of Pericles, his banishment of ten years was revoked. He returned to Athens, reconciled with the party which had defeated him, and so great was the admiration of his magnanimity that all parties generously united in the common cause. Another battle with the enemy was fought in Bœotia, this time attended with success, the result of which was the complete ascendency of the Athenians over all Bœotia. They became masters of Thebes and all the neighboring towns, and reversed all the acts of the Spartans, and established democratic governments, and forced the aristocratical leaders into exile. Phocis and Locris were added to the list of dependent allies, and the victory cemented their power from the Corinthian Gulf to the strait of Thermopylæ. (M473) Then followed the completion of the long walls, B.C. 455, and the conquest of Ægina. Athens was now mistress of the sea, and her admiral displayed his strength by sailing round the Peloponnesus, and taking possession of many cities in the Gulf of Corinth. But the Athenians were unsuccessful in an expedition into Thessaly, and sustained many losses in Egypt in the great warfare with Persia. (M474) After the success of the Lacedæmonians at Tanagra they made no expeditions out of the Peloponnesus for several years, and allowed Bœotia and Phocis to be absorbed in the Athenian empire. They even extended the truce with Athens for five years longer, and this was promoted by Cimon, who wished to resume offensive operations against the Persians. Cimon was allowed to equip a fleet of two hundred triremes and set sail to Cyprus, where he died. The expedition failed under his successor, and this closed all further aggressive war with the Persians.