Spartan Hegemony — Timeline & Key Events

Sparta’s political supremacy never rested on land power alone; it needed a system to translate hoplite success into regional authority. The naval disaster at Cnidus (394 BCE) stripped Sparta of maritime reach, forcing a pivot from triremes to treaties ^[15][1]. The King’s Peace (387/6) provided exactly that: a Persian-written security architecture that granted Asia to Artaxerxes II and proclaimed 'autonomy' for Greek poleis, with violators threatened 'by land and by sea, with ships and with money' ^[2][19]. In effect, Persia supplied the coercive backdrop, Sparta the Greek enforcement ^[12][14].

This interplay of arms and law shaped the decade to 382. Spartan land assets and networks—harmosts, oligarchic allies—did the daily work of control while the treaty’s legitimacy screened interventions ^[1][12]. Yet the same mechanism incentivized overreach: legal dissolution of rival leagues slid into illegal coups like Phoebidas’s seizure of the Cadmeia, defended post hoc as 'useful' ^[3]. When the legal façade cracked, the order reverted to what it had always been: compulsion, now contested by a rejuvenated Thebes with the will and organization to test the 'peace' in battle ^[18][14].

Autonomy in 387/6 was less a city’s freedom than a formula enabling Sparta to police federations. The treaty text is clear and menacing; the King would enforce compliance across the Aegean world ^[2][19]. Its public inscriptions in Greek temples, which Isocrates called a Persian 'trophy,' broadcast a hierarchy: the Great King dictated, the Spartans enforced, the cities obeyed ^[7]. Within this framework, dissolving the Boeotian League or the Argos–Corinth union looked like treaty maintenance rather than partisan intervention ^[12][19].

The Cadmeia coup tore off the mask. By installing a garrison through a surprise seizure and staging a show-trial that executed Ismenias, Sparta converted a legal policy into naked domination ^[3]. That breach of principle forged Theban unity: exiles returned in 379/8, expelled the garrison, and revived a federation that would defeat Sparta in the field ^[3][18]. Later moralists would condemn the Peace as betrayal, but the real indictment was practical: a legal edifice cannot survive if its enforcers treat law as optional ^[20][10].

Sparta’s authority hinged on a belief: its infantry would not break. That belief had withstood shocks—Nemea in 394 reaffirmed Spartan prowess on land even as the fleet sank at Cnidus ^[1][15]. Epaminondas targeted the belief directly by changing the shape of battle: concentrating the Theban left 'not less than fifty shields deep' and pushing superior cavalry ahead to destabilize the Spartan line ^[4][14]. The result was systemic: once the right broke, the myth collapsed, and with it the diplomacy that myth sustained ^[18].

Leuctra shows how tactical innovation can cascade into political realignment. Killing King Cleombrotus I and forcing a truce to collect the dead turned a battlefield win into a reputational rout ^[4][18]. Allies had long tolerated Spartan intrusions because the alternative looked riskier; after Leuctra, the calculus changed. Theban ascendancy was less an inheritance than a proof-of-concept that prestige could be unmade by disciplined geometry and timing ^[14][18].

Greek coalitions ran on reputation as much as tribute. Spartan land victories kept allies onboard despite coercive policies, while the naval loss at Cnidus dented but did not bankrupt the prestige account; the King’s Peace refilled it with Persian credit ^[15][12][19]. Leuctra zeroed the balance in a day. When surviving Spartan officers sought a truce to recover their dead, they broadcast vulnerability—an unmistakable market signal in the economy of alliances ^[18].

Defections followed not only because Sparta lost a king and a battle, but because its enforcement model depended on fear and inevitability. Once neither looked assured, the costs of staying loyal outweighed the gains. The episode underscores a broader mechanism: in multipolar Greece, hegemony was less a fortress than a confidence game, vulnerable to shocks that undermined belief in the hegemon’s reliability ^[14][18][1].

Xenophon’s Constitution ends with decline: wealth concentration, eroding discipline, and dwindling citizen numbers ^[5]. These internal stresses rarely headline narratives of interstate conflict, yet they limit staying power. Fewer Spartiates meant fewer elite hoplites and greater reliance on allies just as Sparta antagonized them through garrisons and legal interventions ^[1][13]. Structural weakness made the polity brittle when shocks arrived.

Diodorus’ moralizing tone—'their own acts of folly'—overstates agency but captures a feedback loop: coercive policies abroad demanded sustained excellence at home; decline at home magnified the costs of coercion abroad ^[10]. When Thebes expelled the Cadmeia garrison and then held firm against invasions in 378–377, Sparta’s capacity to impose outcomes looked fatigued. Leuctra didn’t create crisis; it revealed compounding deficits inside the Lacedaemonian system ^[18][5][13].