military

Liberation of Thebes and Expulsion of the Garrison

Date

-379 — -378

Part of

military

In 379/8 BCE, Theban exiles slipped into the city, assassinated collaborators, and expelled the Spartan garrison from the Cadmeia. Bronze rang on stone as the gates shut behind the retreating harmost. A captive city became a cause.

What Happened

Winter covers conspiracies. From Athens, where exiles had gathered under the colonnades, Pelopidas and his companions returned to Thebes in disguise. They entered houses silently, daggers wrapped in cloth, names memorized. In a series of quick strikes, they killed leading collaborators, including Leontiades, and signaled their allies to seize the moment. The city awakened to shouts—this time not of occupiers, but of neighbors taking back streets [18][3].

The fight for the Cadmeia was brutal and brief. The Spartan garrison, surprised and cut off, negotiated terms rather than face annihilation inside the gray walls. The harmost and his men marched out, shields slung, the sound of their sandals on stone loud in the cold air. Thebes, unburdened, counted its leaders and dead. The scarlet that had crowned the acropolis vanished into the winter road toward the Peloponnese [3].

Athens played a quiet role. The city had harbored exiles and looked the other way as preparations advanced. In the aftermath, Athenians and Thebans understood each other better: both had seen Spartan power up close—Athens in 404, Thebes in 382—and both now had reasons to resist the ‘autonomy’ enforced from Laconia [18].

The liberation reversed a decade’s logic. Legally, Thebes had been ‘autonomous’; practically, it had been occupied. The knife-edge between the two snapped. The next step came quickly: in 378, Thebes reorganized Boeotia under a renewed federation, aligning towns behind a program of defense and reform. The oaths that had been scattered by Spartan commissioners were rewritten and sworn again [18][20].

Sparta responded with invasion. In 378 and again in 377, Peloponnesian armies moved through the passes into Boeotia, only to find improved Theban cavalry, fortified lines, and a countryside that now fought with purpose. A city that had once submitted to a surprise coup became one that could repel organized campaigns [18].

Why This Matters

The liberation of 379/8 reanimated Theban politics and Boeotian regionalism. It expelled a Spartan garrison, destroyed a client regime, and demonstrated that the King’s Peace had lost moral authority in the very city it claimed to secure. It also solidified a Theban-Athenian understanding that would shape alliances through the 370s [18][3].

The event clarifies autonomy as a weaponized principle: a word used to dismantle the Boeotian League now motivated Theban claims to self-rule and collective defense. Once Thebes retook the Cadmeia, the push to reconstitute the federation in 378 followed naturally, giving institutional shape to a military resurgence [12][18].

In the broader arc, the liberation set up the decade’s climactic confrontation. The Boeotian War began de facto with this act; repulsed invasions in 378–377 proved the shift in local balance; and by 371 the legal wrangles over who could sign ‘for Boeotia’ at a peace conference would send a Spartan army under Cleombrotus into a trap at Leuctra. The sound of sandals leaving the Cadmeia became, in time, the silence over Spartan dead on the field in 371 [18][14].