The Theban–Spartan War of 378–362 BC was a series of military conflicts fought between Sparta and Thebes for hegemony over Greece. In 378 BC, led by General Epaminondas, Thebes revolted against its Spartan garrison and successfully repelled Spartan offensives. A clever tactician, Epaminondas crushed the hitherto invincible Spartan army at Leuctra in 371 BC, thereby ending Sparta's hegemony and starting Thebes' own hegemony over Greece. After Leuctra, the war continued in the Peloponnese, where Sparta was fighting for survival. In 362 BC, the Battle of Mantinea was a new victory for Thebes, but Epaminondas was also killed. The conflict ended soon after with a treaty of general peace signed by all the belligerents, except Sparta, which was by now isolated and permanently weakened.
Background
Sparta had emerged victorious from the Peloponnesian War against Athens (431–404 BC), and occupied a hegemonic position over Greece. However, the Spartans' violent interventionism upset their former allies, especially Thebes and Corinth. The resulting Corinthian War (395–387 BC) ended with a difficult Spartan victory, but the Boeotian League headed by Thebes was also disbanded.
After the end of the Corinthian War, which had seen many of Sparta’s allies abandon her, Sparta began reconstructing its hegemony and punishing many disloyal allies. In 385 BC Sparta attacked Mantinea claiming they had failed to fulfil their allied obligations. When Sparta took the city they split it into four settlements, as that was what it had used to be. In the north the city of Olynthus grew in power and violated the terms agreed upon at the end of the Corinthian War. Because of this Sparta sent an army against the city under the command of Phoebidas. When the army was in Boeotia around 383 or 382 BC, Leontiades, who was leader of the oligarchic party in Thebes, asked Phoebidas to occupy the Theban Citadel as Leontiades felt threatened by the democratic party. The Spartans were ruled by kings and, therefore, were supportive of oligarchic governments in other Greek cities. Because of this Phoebidas agreed, occupying the city and practically taking control of Thebes.
Upon the seizure of the Theban citadel by the Spartans, Pelopidas and other leading Theban democrats fled to Athens where Pelopidas took the lead in a conspiracy to liberate Thebes. In 379 BC the democratic party surprised and killed their chief political opponents in Thebes (members of the aristocratic party that supported the Spartans), and roused the people against the Spartan garrison, which surrendered to an army gathered by Pelopidas.
379/378 BC – Theban coup
The defeat of the pro-Athens forces and the triumph of Sparta in the preceding Corinthian War (394–386 BC) was especially disastrous to Thebes, as the general settlement of 387 BC, called the Peace of Antalcidas or "King's Peace", stipulated the complete autonomy of all Greek towns and so withdrew the other Boeotians from the political control of Thebes. The power of Thebes was further curtailed in 382 BC, when a Spartan force led by Phoebidas occupied the citadel by a treacherous coup de main. When the Theban citadel was seized by the Spartans (383 or 382 BC) with the help of their aristocratic supporters in the city-state, who killed the democratic leader Ismenias and forced his aristocratic allies to run away from the city with hundreds of their supporters. Pelopidas and other leading Theban democrats fled to Athens where, years later, the Theban polemarch Leontiades sent assassins to prevent the exiles from returning; the assassins only managed to kill the democratic leader Androcleides. Pelopidas took the lead in a conspiracy to liberate Thebes by killing the oligarchs.
Meanwhile, in Thebes, Epaminondas began preparing the young men of the city to become warriors, giving them a proper training despite their social rank. In the winter of 379 BC, a small group of the exiles, led by Pelopidas, infiltrated the city. They then assassinated the leaders of the pro-Spartan government, and supported by Epaminondas and Gorgidas, who led a group of young men and surrounded the Spartans on the Cadmeia. Pelopidas and allies managed to kill Leontidas and his aristocrat allies. The following day, Epaminondas and Gorgidas brought Pelopidas and his men before the Theban assembly and exhorted the Thebans to fight for their freedom; the assembly responded by acclaiming Pelopidas and his men as liberators. The Cadmeia was surrounded, and the Spartans attacked; Pelopidas realised that they must be expelled before an army came from Sparta to relieve them. The Spartan garrison eventually surrendered on the condition that they were allowed to march away unharmed. The narrow margin of the conspirators' success is demonstrated by the fact that the Spartan garrison met a Spartan force on the way to rescue them as they marched back to Sparta. Plutarch portrays the Theban coup as an immensely significant event:
...the subsequent change in the political situation made this exploit the more glorious. For the war which broke down the pretensions of Sparta and put an end to her supremacy by land and sea, began from that night, in which people, not by surprising any fort or castle or citadel, but by coming into a private house with eleven others, loosed and broke in pieces, if the truth may be expressed in a metaphor, the fetters of the Lacedaemonian supremacy, which were thought indissoluble and not to be broken.
Boeotian War
The Boeotian War broke out in 378 BC as the result of the revolt in Thebes against Sparta. The war saw Thebes become dominant in the Greek world at the expense of Sparta. However, by the end of the war, Thebes’ greatest leaders, Pelopidas and Epaminondas, were both dead and Thebes' power already waning, allowing for the rise of Macedon.
Outbreak (378 BC)
Sparta immediately sent against Thebes a force under one of their kings, Cleombrotus, in the middle of winter. As the border fort of Eleutherae was held by an Athenian garrison, he was forced to enter Boeotia through Mount Cithaeron, where he wiped out a force of Theban democrats. After passing through the allied cities of Plataea and Thespiae, Cleombrotus's force camped at Cynoscephalae (6 km west of Thebes) to await events. The Athenians were alarmed at Cleombrotus's presence nearby, and, seeking to placate Sparta, immediately punished their own generals who had aided the Theban coup. It was probably around this time, likely due to fear that Athens would not offer support, that Thebes sent an embassy to Sparta, offering to rejoin the Peloponnesian League in return for recognition of its new government. Cleombrotus inflicted no damage to Theban territory, as he apparently hoped for a reconciliation, but the government at Sparta, led by the other king, the anti-Theban hardliner Agesilaus, would have nothing less than the punishment of the coup leaders and the restoration of a pro-Spartan regime, terms which Thebes rejected.
Whatever negotiations Cleombrotus may have initiated on his own came to nothing, and, once it became apparent after 16 days that neither Thebes nor Athens would offer a challenge, he ended the campaign, retiring unhindered by way of Creusis and Aigosthena. Although Athens had not yet committed itself, it was soon the target of an act of Spartan aggression which brought it firmly to the Theban camp. Sphodrias, the harmost (governor) whom Cleombrotus had left in command of a Spartan remnant garrisoned at Thespiae, launched an officially unauthorized nighttime raid on the Athenian port of Piraeus. The attack was a fiasco, as the Spartans were still a distance away from their objective when dawn broke, and Sphodrias had to content himself with plundering the Attic countryside while retreating. According to varying accounts, Sphodrias had either been enticed by a Theban bribe, aimed at forcing Athens to become more belligerent, or acted upon secret orders from Cleombrotus. A Spartan delegation in Athens, which had been probably sent earlier by Agesilaus to assess Athenian intentions, professed ignorance of the attack, but Sphodrias was then unexpectedly acquitted by the home government. Athens declared that Sparta had broken the peace and prepared for war.
Invasions of Agesilaus II
Sparta called upon all its allies and, led by Agesilaus, invaded Boeotia in the spring of 378. The Thebans and their commander, Gorgidas, had decided to resist the Spartans and screen their city by setting up, probably with aid of the Athenians, a continuous trench and palisade that stretched from the border with Thespiae in the west, alongside the northern bank of the Asopus in the south, to the border with Tanagra in the east.
The Sacred Band first saw action in 378 BC, at the beginning of the Boeotian War. It was during the famous stand-off between the Athenian mercenary commander (and later strategos) Chabrias (d. 357 BC) and the Spartan King Agesilaus II (444 BC–360 BC). Prior to the creation of the Sacred Band under Gorgidas, the Athenians had helped the Theban exiles retake control of Thebes and the citadel of Cadmea from Sparta. This was followed by Athens openly entering into an alliance with Thebes against Sparta. In the summer of 378 BC, Agesilaus led a Spartan expedition against Thebes from the Boeotian city of Thespiae (then still allied to Sparta). His force consisted of 1,500 cavalry and 28,000 infantry. At least 20,000 of the infantry were hoplites, while 500 were of the elite band of Sciritae (Σκιρῖται) light infantry vanguard. Learning of the impending invasion, Athens quickly came to the aid of Thebes by sending a force of about 200 cavalry and 5,000 men (both citizen and mercenary, including hoplites and peltasts) under the command of the Athenian strategos Demeas and mercenary commander Chabrias.
Agesilaus probed the stockade looking for weak points, moving his camp around it and devastating the land outside, while the Thebans and Athenians sent out repeated forays to harass his forces. After getting a measure of the defenders' movements and having them grow used to his own movements, the King surprised them by marching at daybreak and crossed the stockade at an undefended position before the enemy could reach him. Agesilaus then encountered a Theban and Athenian force set up on a defensive position in a hill some 3+1⁄2 km southwest of Thebes. He dispersed their light troops and brought his army uphill to threaten the enemy, but the latter, led by the Athenian Chabrias, defiantly stood their ground in a defensive and provocative manner. Gorgidas and the Sacred Band occupied the front ranks of the Theban forces on the right, while Chabrias and an experienced force of mercenary hoplites occupied the front ranks of the Athenian forces on the left. Agesilaus first sent out skirmishers to test the combined Theban and Athenian lines. These were easily dispatched by the Theban and Athenian forces, probably by their more numerous cavalry. Agesilaus then commanded the entire Spartan army to advance. He may have hoped that the sight of the massed Spartan forces resolutely moving forward would be enough to intimidate the Theban and Athenian forces into breaking ranks. The same tactic had worked for Agesilaus against Argive forces in the Battle of Coronea (394 BC). It was during this time that Chabrias gave his most famous command. With scarcely 200 m (660 ft) separating the two armies, Agesilaus was expecting the Theban and Athenian forces to charge at any moment. Instead, Chabrias ordered his men to stand at ease. In unison, his mercenary hoplites immediately assumed the resting posture—with the spear remaining pointing upwards instead of towards the enemy, and the shield propped against the left knee instead of being hoisted at the shoulders. Gorgidas, on seeing this, also commanded the Sacred Band to follow suit, which they did with the same military drill precision and confidence. The audacity of the maneuver and the discipline of the execution was such that Agesilaus halted the advance.
Unwilling to charge uphill against a strong opponent, Agesilaus decided not to engage the enemy and, his bluff called, continued devastating Theban territory, reaching the walls of the city itself.