Thebes at first found herself isolated; and it seemed to everyone that his resistance to the Spartans could not last long. Indeed, the Corinthian war seemed to have shown that Sparta, with the moral and financial support of Persia, was in the invincible peninsula. But conforming to the very nature of its dominance, based on force, Sparta, seeking to consolidate it with acts of brutal arrogance, hastened its ruin, which it was heading for by its very nature. Thus, in order to better ensure Athenian neutrality, the Spartan Sfodria, in full peace, attempted by surprise to occupy Piraeus. The surprise did not succeed, but the Athenians, even after that eager for peace, were forced into war by the refusal of any satisfaction, which, if it may have had small origins of a private order, it essentially came from the very logic of Spartan politics. Athens responded by allying with Thebes and reconstituting its maritime league (377). He reconstituted it with new criteria, ensuring the full autonomy of the allied cities and thereby avoiding being in conflict with the peace of Antalcida. He renounced cleruchies and jurisdiction and even private possessions in the territory of the league and naturally excluded the Greek cities of Asia belonging to the Great King. Southern Thrace joined the league; also Thebes, Euboea, Jason of Fere and, in the west, Epirus and the powerful Corcira. Governing body of the league was a federal diet that met in Athens; the fixed taxes were replaced by contributions, the amount of which was fixed by the diet. Sparta tried to oppose the Athenian progress, but the naval victory of Cabria near Naxos (376) destroyed the last remnant of the Spartan maritime power in the Aegean. And yet Athens longed for peace, and the consolidation and extension of the power of Thebes to the borders of Attica did not fail to arouse her apprehensions. So, with the Persian mediation, negotiations were reached, and in 375 a peace was reached between Sparta and Athens, which, however, incidents that arose in the Ionian Sea, where precisely at that time Athens was trying to extend its league, disturbed as soon as it was concluded. The one who took advantage of this renewed hostility was Thebes, who now reunited Boeotia under its dominion almost entirely, reconstituting, with a more solid organism, the league that the peace of Antalcid had destroyed. This meant that Sparta and Athens came together again and that in a congress held in Sparta in 371 the general peace was concluded. Peace recognized the new Athenian league, founded on the principle of autonomy, but in the mind of the Spartans, from which it was promoted, it aimed to destroy the Boeotic league, which was not founded on that principle. So when Epaminondas, the Theban delegate, asked to sign in the name of the Boeotians, Agesilaus, with the implicit consent of all the other signatars, did not want to allow it, and Thebes was excluded from the peace. With a realistic view of the general conditions, as in 386 he had renounced Asia, so now Sparta recognized that it could not prevent the reconstitution of the Athenian maritime league, that is, the return of Athens to great power as it was before the Peloponnesian War. But he considered himself strong enough to reaffirm, after these concessions, his dominance in the rest of Greece. It was for his part only a question of strength, and by now everyone foresaw the fall of Thebes. But the Thebans knew they were fighting for existence; and they also had a genial general in Epaminondas, who, against the tight attack of the Peloponnesian phalanxes, opposed the new tactic of the oblique order (v.epaminondas). The effect was the unexpected victory that the Thebans won at Leuctra (371). Immediately the Spartan hegemony, founded on force, undermined by that principle of autonomy that it proclaimed, fell apart. In the Peloponnese itself the democratic spirit, hitherto violently compressed, rose up with unprecedented violence. It triumphed in Arcadia which, breaking away from Sparta, was constituted on the example of Boeotia as a unitary league. Epaminondas, intervening in the Peloponnese in favor of the anti-partan movement, invaded Laconia and put Sparta itself in danger for a moment. Then, calling the Messenî to freedom, he gave them a center in the city of Messene, founded by his initiative on the slopes of Mount Itome (369). Thus the Peloponnesian unity was broken only to be reconstituted if not, in completely different contingencies, by the Achaeans, and the Peloponnese ceased to have that preponderant part in Greek history that it had had since the middle of the century. A preponderant part to which the great victory over the Persians was due above all, but it was also due, in the course of the following century, to the wearing out of the Greeks in internal struggles, in which Sparta, scarcely participant in the progressive civil movement, had he supported for his own benefit the two lingering principles of the oligarchy and the isolation of individual cities, striving to make history go backwards, which directed Greece towards freer forms of government and ever more intimate associations between city and city.

In the years that followed, Thebes established his hegemony in central Greece, excluding Attica, and in Thessaly, where he fought with various fortunes (particularly notable in military respect the battle of Cinoscephalus, in which Pelopidas fell, 364), but ended with to firmly establish one’s dominance. This dominance Epaminondas tried to extend also on the sea, having a fleet built and leading it, without the Athenians daring to fight it, up to the Propontis, where he gained Byzantium to the Boeotic alliance (364). But it was a hegemony which did not implement any new principle and, empty of any ideal, was also based solely on strength. The decisive step, which could make it stable, that of transforming the Boeotic league renewed by a cantonal league into a larger and more progressive organism, calling to join cities that would accept Boeotic hegemony outside the Boeotian terms, not only was not done, but was not even thought of; and this precisely, although similar tendencies had already manifested themselves elsewhere in Greece, due to the cultural inferiority of the Boeotians, which rendered them powerless to innovate initiatives in the field of politics. The dissolution of the new hegemony was in germ in this very act. Which, on the other hand, had only a short and opposed life. The accession of Euboea to the Boeotians, the occupation made by them of Oropo (366) on the border of Attica, the attempt to found a maritime power, had increasingly separated it from Athens, who had come back to Sparta and had ended up forming an alliance with it. Even the Arcadian league, which had given itself a new center in Megalopolis (368), had failed to ensure its stability. It was one of the least advanced regions of Greece, and it is understood that the unitary movement found an effective contrast in the cantonal interests, especially since Sparta was always ready to stir up dissensions. Precisely the collapse of the Arcadian league, from which Mantinea broke off allying himself with Sparta, gave occasion to the last intervention of Epaminondas in the Peloponnese. This intervention ended with the battle of Mantinea, in which Epaminondas, fighting against the Athenians, the Spartans and their allies, prepared for that victory that his death on the field prevented from being achieved (362).

The shattering of hegemonies. – The battle of Mantinea was followed by a general peace, demonstrating more than anything else the inability of the contenders to resolve the dissensions that troubled Greece with arms. Sparta, which did not want to recognize the freedom of the Messenî, was excluded from peace, but reduced to impotence and effectively put out by the great Greek politics. Athens, exhausted by the long struggles, had had to witness serious defections in the bosom of the renewed maritime league, which it had not managed to keep intact, although at the head of its armies were in those years some of its greatest men of war: Cabria, Ificrate and Timothy, the son of Conon. This new league had come again, like the first, transforming into an empire without this transformation having the relative justification that the struggle against the barbarian had given it during the pentecontaetia; and the tiredness and the lack of that enthusiasm, which had animated the Athenians in the century. V, explain how every innovative audacity was renounced by not taking any more steps on that path, for which Athens had momentarily set out after the battle of Egospotami with the granting of citizenship to the Samî. Stronger in appearance, but only in appearance, was the federation that was gathering around Thebes. No ideal reason, no material advantage drove the Phocians and the Thessalians to shed their blood for Boeotic hegemony. And as for the attempt to extend Boeotic supremacy over the sea, it was certainly dropped after the death of Epaminondas. It was evident that no advantages could be drawn from it, which would compensate for the expenses necessary to set up an army, especially in a country as alien to maritime traffic as Boeotia. On the other hand, in the bosom of the Boeotic league proper, even before the death of Epaminondas, separatist ambitions had been felt and were violently repressed, with the destruction of Orchomenus.