The Theban Hegemony (371-362) was a short period in which the battlefield victories of Epaminondas overthrew the power of Sparta, and made Thebes the most powerful state in Greece. It began with the crushing Theban victory over a Spartan army at Leuctra, and effectively ended with the death of Epaminondas at the battle of Mantinea.
In 382 a passing Spartan army had seized the citadel of the Cadmea and imposed a pro-Spartan dictatorship on Thebes. This was overthrown in 379 by a revolt in Thebes, supported by exiles returning from Athens. After the Spartans were expelled the capable military leaders Epaminondas and Pelopidas came to the fore. This led to a general war (Theban-Spartan or Boeotian War), with Athens siding with Thebes against Sparta. In 371 this wider war was ended at a peace conference, but Thebes herself was excluded from the peace after the Athenians and Spartans insisted that the members of the Boeotian League should be represented individually while Epaminondas insisted that they were represented by the Boeotian League. The Thebans were excluded from the peace treaty and left to face Sparta without allies.
The Spartans reacted by invading Boeotia from the west. At Leuctra (371) they suffered a crushing defeat after Epaminondas adopted a novel tactical plan, massing most of his men in a 50-deep phalanx on his left, and using it to crush the thinner Spartan right. King Cleombrotus of Sparta was killed in the battle, which was the first major battlefield defeat for the Spartan infantry in a full scale battle.
Crisis for Sparta
News of the defeat at Leuctra triggered a series of changes in the Peloponnese. At Sparta the news was greeted with a mobilization of the remaining men, who were sent to rescue the army, but the Thebans also gained allies, in this case Jason of Pherae. The surviving Spartans at Leuctra agreed to a truce and withdrew back towards home, meeting the relief army on the way. Once the survivors returned home, the Spartans wisely decided that there were too many of them to ostracise, and decided to ignore their normal laws just for that day,
At Argos there was a dramatic democratic revolution, in which over 1,200 of the wealthiest citizens were killed.
The Mantineans, whose city had been split up by the Spartans in 384 BC regrouped and rebuild the city. King Agesilaus was sent to try and convince them not to, but unsurprisingly he failed.
At Tegea a civil war broke out between the pro-Spartan oligarchy and anti-Spartan democrats. Mantinea intervened on the side of the democrats, and the victors then founded a new Arcadian League.
Late in 370 BC the Spartans attacked Mantinea, on the grounds that their intervention at Tegea broke the terms of the peace of 371. The newly formed Arcadian League came to the aid of Mantinea, as did Argos and Elis. The Arcadians also attempted to gain an alliance with Athens, but were turned down, and then successfully negotiated an alliance with Boeotia.
While these diplomatic efforts were underway Agesilaus invaded Arcadia and established a base at Eugaea. Another Spartan commander, Polytropus, fought off an attack on Orchomenus, but was then defeated and killed while pursuing the attackers. Agesilaus attempted to provoke a battle in the territory of Mantinea, but the Arcadians refused to fight until their new Boeotian allies had arrived. Agesilaus decided to pull back to Sparta instead of risking a winter campaign. The Arcadians took advantage of his absence to attack Heraea in western Arcadia, before the Boeotian army arrived, under the command of Epaminondas.
Epaminondas in the Peloponnese
The Allies now made one of the most important decisions of the war. Although the direct threat to Arcadia was over, the allies decided to invade Laconia. The allies attacked along four routes, and managed to break into the valley of the Eurotas, after defeating several of the Spartan border forces. The allies marched south, and came dangerously close to Sparta itself before eventually retiring into Messenia, after failing to take Sparta, which was vigorously defended by Agesilaus. Even so this direct threat to a city that had been unthreatened for so long that it had no walls must have been a real psychological blow to the Spartans.
Sparta still had some allies in the north-east of the Peloponnese, and they landed on the coast east of Sparta during this campaign, but they were unable to prevent the Boeotians from re-founding the long-destroyed state of Messenia. A new city of Messene was founded, and a major building block of Spartan power was cut away. The helots of Messenia had played a major part in supporting the full Spartan citizens since the area was conquered over two centuries earlier. The campaign of 370-369 was thus just as significant as the battle of Leuctra. There was some good news for Sparta - Athens now saw Thebes as the bigger threat, and formed an alliance with her former enemy.
The Boeotians and Epaminondas returned to the Peloponnese for a second campaign in 369. This time they captured Sicyon and probably Pellene, but were repulsed at Troezen, Epidaurus and Corinth. Athenian troops played a part in the defence of Corinth.
Persia had been a major factor in Greek politics in the later stages of the Great Peloponnesian and Corinthian Wars, but by this point the authority of Artaxerxes II was coming under attack. In the winter of 369/8 Philiscus, an envoy from the satrap Ariobarzanes arrived in Greece, probably to raise mercenaries for his master, who would soon revolt against Artaxerxes (Satrap's Revolt). While he was in Greece Philiscus attempted to broker a peace, but talks at Delphi failed after the two sides couldn't agree on the future of Messene. When Philiscus left Greece he left behind 2,000 mercenaries, who entered Spartan service.
The Spartans did win some successes during this period, including the 'Tearless Battle' of 368 in Arcadia, in which a Spartan army led by the future Archidamus III was said to have suffered no casualties. This came after the Spartans invaded the south-west of Arcadia. The Arcadians, with support from Argos and Messenia, intercepted and trapped the Spartans, but were then defeated. However the Spartans weren't strong enough to take advantage of their victory, and later in the same year the Arcadians founded a new fortified capital at Megalopolis. The Spartans were now faced with three new fortified obstacles to any campaigns in the Peloponnese - Megalopolis, Messenia and Mantinea.
In 367 Artaxerxes of Persian probably officially sided with Thebes, after the Thebans sent envoys to his court at Susa.
367 also saw the Thebans campaigning against Alexander, tyrant of Pherae in Thessaly. In the previous year Pelopidas, one of the Liberators of Thebes, had been captured by Alexander, and a second army had to be sent to rescue him. Epaminondas served in this army as a common soldier, but had to be promoted to command it after the army got into trouble. He was able to rescue the army, but had to return in the spring of 367 with a second army. After a careful advance Alexander agreed to a 30 day truce and released his prisoner.
Early in 366 Thebes attempted to organise a peace congress, but the attempt failed as nobody wanted to swap Theban dominance for the older Spartan or Athenian models. Part of the problem was that Thebes was trying to impose terms that they had already agreed with the Persians, an approach that was always likely to cause anger in Greece.
In 366 Epaminondas led his third expedition into the Peloponnese. This time his target was Achaea, in the north of the Peloponnese. This area had remained neutral, but the arrival of the Boeotians and Arcadians convinced the oligarchies of Achaea to side with them, in return for being allowed to stay in power. This settlement was unpopular in Boeotia, and Epaminondas was overruled. New democratic regimes were installed, but the exiled oligarchies quickly overthrew them, and Achaea became a Spartan ally.
366 also saw an example of the often confused state of diplomacy in Greece. Although Athens was an ally of Sparta, she wasn't at war with Thebes. In 366 a Theban ally on Euboea attacked Oropus, an Athenian possession on the island. The Athenians sent a force to reclaim the place, but Thebes moved first and occupied the city. Athens agreed to submit the case to legal arbitration, and lost the case. In the aftermath of this case the Athenians then entered into an alliance with the Arcadians, where the Boeotian alliance had already come under strain. Athens was now allied with Sparta and in a defensive alliance with Sparta's active enemies in Arcadia.
Over the winter of 366-365 the diplomatic picture was further muddied when Sparta's allies at Corinth asked for, and were granted, permission to make peace with Thebes. A number of other Peloponnesian cities also made peace at about this time, effectively ending the Peloponnesian League. After this round of diplomacy Sparta was at war with Arcadia, but allied with Achaea. Arcadia could still rely on her Boeotian allies and the Messenians.
In 365 in the Peloponnese a conflict broke out between Elis and the Arcadian League, over the border territories of Lasion and Triphylia. This was made more important because Olympia was within the territory of Elis. Athens provided support for the Arcadians under the terms of their recent treaty, as did Boeotia and Argos.
In 365 Archidamus captured the Arcadian city of Cromnus, in an attempt to control the route between Sparta and their new allies at Elis. The Arcadians then besieged the city, and Archidamus was wounded during a failed attempt to lift the siege. This conflict between Elis and the Arcadian League appears to have ended after a battle in the Sanctuary at Olympia during the 104th Games in 364.
The war with Elis eventually triggered a split within the Arcadian League. As a result of their successes, the Arcadians had been able to set up a new puppet state of Pisatis, which included Olympia. The funds in the Olympic treasury were then used to pay for the standing army of the League. Mantinea objected to this, and was able to convince the League's Assembly to forbid the practise. At about the same time the Assembly voted in favour of peace with Elis. More conservative league officials combined with the local Theban commander to try and arrest the leading members of the assembly but failed. The Theban commander was sent home and an official protest made about his conduct. Epaminondas was angered by the peace moves, and threatened to invade Arcadia.
In 364-363 Epaminondas raised a Theban fleet, and campaigned as far north as the Bosporus, threatening Athens's grain supplies from the Black Sea. He aimed to win over Rhodes, Chios and Byzantium, and did manage to convince Byzantium to abandon her Athenian alliance, but otherwise the great naval effort had limited impact and the fleet wasn't involved in any more major expeditions.
In 364 the Thebans had to intervene in Thessaly, where Alexander of Pherae was becoming dangerously powerful. His opponents asked for Theban help, and Thebes agreed to send an army commanded by Pelopidas. This army was then disbanded after a solar eclipse, but Pelopidas decided to set off anyway at the head of a small force of volunteers. He joined with his Thessalian allies and defeated Alexander at the battle of Cynoscephalae, but was killed during the fighting. Thebes had thus lost the first of her great leaders of this period. In response a second Theban army was dispatched, and a second battle was won. Alexander was forced to become an Ally of Thebes and to give up his recent conquests.
The split in the Arcadia League ended up triggering Epaminondas's last invasion of the Peloponnese. The League split into an anti-Theban faction led by Mantinea, which allied with Elis, Achaea and Sparta, and asked for help from Athens, and a pro-Theban faction, which included Tegea and Megalopolis, and allied with Argos, Sicyon, Messenia and Boeotia.
Epaminondas led his army south in 362, at one point coming very close to capturing Sparta itself. He then withdrew towards Mantinea, where he ran into an army with contingents from Sparta, Athens, Elis and northern Arcadia. Epaminondas had Thebans, southern Arcadians, Messenians and Argives. The resulting battle of Mantinea was Epaminondas's final victory, for he was killed in the battle, despite having broken the Spartan battle line once again.
Peace and Stalemate
This effectively ended the war. Thebes had lost both of her leaders and was now exhausted, as were most of her rivals. A period of uneasy peace followed, with no power dominant in mainland Greece. Only Sparta didn't agree to the peace treaty of 362, because she was unwilling to recognise the independence of Messenia, but the Spartans were also too drained to disturb the peace. Messenia herself was a signatory of the peace.
Although Thebes was no longer a great power after Mantinea she was still more powerful and influential than she had been before the battle of Leuctra, and would remain a major power within Greece until the rise of Macedonia. Sparta was greatly weakened by the war. The loss of Messenia reduced the number of helots under her rule, and thus the number of Spartiates that could be supported, while the foundation of Megalopolis and the restoration of Mantinea meant that she was surrounded by strong opponents. Only Athens emerged from the period with her power undamaged, a remarkable achievement for a city that appeared to have been crushed only forty years before.
As was so often the case in Ancient Greece, the peace of 362 BC was short lived. The Athenians soon overstepped the mark in their new league, triggering the Social War of 357-55 BC. This was immediately followed by the Third Sacred War (355-346 BC), which saw the rise of Philip II of Macedonia.