The first years after the Peloponnesian War are marked by Spartan hegemony. However, the hegemony of Sparta from the very beginning caused acute discontent in the Hellenic world. Like Athens, Sparta imposed phoros on its allies. Constantly interfering in the internal life of Greek cities, Sparta everywhere persecuted democrats and imposed the power of oligarchs. Many cities were garrisoned by Spartan governors. Thus, the Greek poleis, which had expected Sparta to liberate them, found themselves in worse conditions than during the Athenian Union.
The situation of Sparta was greatly complicated when its relations with Persia soured. Receiving subsidies during the Peloponnesian War, Sparta promised to return the Greek cities of the Asia Minor coast to Persia in case of victory. However, the Greek cities of Asia Minor gained their independence as a result of the Greco-Persian wars, which were perceived by most Greeks as a heroic past. Sparta did not immediately decide to encroach on this independence. Therefore, she did everything possible to delay the fulfillment of her obligation.
After the death of the Persian king Darius II, a struggle for the throne began between his eldest son and heir Artaxerxes and the younger Cyrus. Cyrus turned for help to Sparta, with which he had been closely associated since the Peloponnesian War. It was advantageous for Sparta to support Cyrus, because as compensation for its support, it could bargain for the preservation of the independence of the cities of Asia Minor. Having recruited a 13,000-strong Greek mercenary force and joined them with his Persian troops, Cyrus launched a campaign against Artaxerxes. However, in 401 BC. at the Battle of Cunaxa (north of Babylon) Cyrus was killed. Cyrus ' native troops immediately went over to the side of Artaxerxes, while his Greek mercenaries, who by this time were only a little more than 10 thousand, were far from their homeland surrounded by enemies. In addition, the commanders of the Greek detachments invited to the camp of Artaxerxes, ostensibly for negotiations, were treacherously slaughtered. Then the Greeks elected new military leaders, one of whom was the historian Xenophon, who described this campaign, and began to retreat north to the Black Sea coast. Despite all the efforts of the Persians to prevent the campaign and the difficulties of the way, the Greeks still fought their way to the sea and managed to return to their homeland, losing, however, about a quarter of their composition.
Regardless of the outcome of this retreat, Sparta's position was not easy. Artaxerxes was very annoyed by the performance of Sparta on the side of Cyrus. The satrap Tissaphernes demanded that the Greeks of Asia Minor pay tribute, i.e., recognize themselves as subjects of the Persian king. In this situation, Sparta was forced to support the Greeks of Asia Minor.
After the Peace of Antalkida, Spartan hegemony in Greece was briefly restored. However, the subsequent course of events showed that the policy of rough pressure and interference in the internal affairs of other Greek states, which was strictly carried out by Sparta, was only able to alienate even its old allies. In this connection, the events that took place in 379 BC in Thebes have acquired significant significance. Here, the oligarchs were in power, who enjoyed the support of a Spartan garrison of one and a half thousand located in the Theban acropolis of Cadmaeus. Many of the Theban Democrats were forced to flee to Athens and other cities; some remained in Thebes, but went into hiding. However, among the urban demos and Boeotian peasantry, dissatisfaction with the existing order grew stronger and stronger. The democratic movement was led by Pelopidas. The rebels ' hatred of the oligarchic regime was so great that the Theban oligarchs were slaughtered, and the Spartan garrison was forced to capitulate.
From this time on, the rise of Thebes begins. Other Boeotian cities were united around them; in defiance of the Peace of Antalkida, the Boeotian League was re-organized. Athens soon began to maintain friendly relations with this alliance, hoping to find support in it against Sparta.
In 378 BC, under the leadership of Athens, the second Athenian Naval Alliance was formed. It included many states that had previously been allies of Athens, but in terms of the number of participants, this union could not be compared with the first. For example, the cities of Asia Minor that fell under the rule of the Persians, and a number of others, did not participate in it. When organizing the second naval alliance, both the Athenians and their new allies took into account the experience of the past: the alliance was built on more or less equal principles. An interesting inscription is a decree of the Athenian ecclesia on the structure of this association: fearing that the allies might suspect them of seeking to restore their power, the Athenians swore that they would not exact Phoros from the allies, would not interfere in their internal affairs, would not send them any officials, garrisons, or, especially, clerks. In order to equip and maintain the fleet, the Athenians were forced to mobilize internal resources and carry out a reform, according to which the first three categories of citizens had to pay a special tax annually, the so-called eisfora, according to the size of their property.
The formation of the second Athenian naval and Boeotian alliances was not without reason regarded by Sparta as a real threat to its hegemony. Therefore, the Peloponnesian fleet was sent to the coast of Attica to block them. Soon, however, the Peloponnesian fleet suffered a heavy defeat in the naval battle of Naxos (376 BC). After that, the Spartans threw their main forces into the fight against Thebes. In 371 BC, the famous battle of Leuctra was fought in Boeotia. The Theban forces were commanded by the outstanding general Epaminondas, who in this battle for the first time used a new formation, the so-called oblique wedge. The essence of the innovation was the unusual strengthening of the right flank for that time, which decided the outcome of the battle. The Spartan army suffered a crushing defeat.
The defeat of the Spartans and the subsequent campaigns of the Thebans in the Peloponnese caused a general rise in the democratic movement throughout Greece. A number of democratic upheavals are taking place in the Peloponnese itself. In a previously backward area like Arcadia, a strong democratic alliance was formed under the leadership of the city of Mantinea. Messenia becomes independent. The result of all these upheavals was the complete collapse of the Peloponnesian Union, the loss of Sparta's position as a hegemon and its transformation into a secondary state.
However, the rise of Thebes was very short-lived. Boeotia had even less opportunity to occupy a leading position in the Hellenic world than Sparta. In addition, the balance of power in Greece changed dramatically when the Athenians, frightened by the excessive strengthening of Thebes, withdrew from them and united with Sparta. Epaminondas launched a new campaign in the Peloponnese, and in 362 BC a decisive battle took place at Mantinea between the Spartan and Theban forces. The Thebans again won a brilliant victory, but were unable to realize its results due to extremely large losses and the death of Epaminondas. Thebes ' forces were already exhausted, and they could no longer maintain hegemony in the Peloponnese. Athens, meanwhile, tried to take advantage of this favorable situation and return to its old great-power policy towards its allies. But the revival of this policy led to the so— called Allied War (357-355), which resulted in the collapse of the second Athenian naval alliance.