Battle of Cynossema

Part of the Peloponnesian War

Date	411 BC
Location	Off Cynossema, in the Thracian Chersonese
Result	Athenian victory

Belligerents

Athens

Sparta

Commanders and leaders

Thrasylus,
Thrasybulus

Mindarus

Strength

76 ships

86 ships

Casualties and losses

15 ships

21 ships

The naval Battle of Cynossema (Ancient Greek: Κυνὸς σῆμα) took place in 411 BC during the Peloponnesian War. In the battle, an Athenian fleet commanded by Thrasybulus and Thrasyllus, although initially thrown on the defensive by a numerically superior Spartan fleet, won a narrow victory. This victory, coming as it did at a time when Athens' traditional democratic government had been replaced by an oligarchy, and when an Athenian defeat could have ended the war, had an impact out of proportion to its tactical significance. The newly confident Athenian fleet proceeded to win two more victories in the Hellespont in quick succession, the second being the dramatic rout at Cyzicus, which ended the immediate Spartan threat to Athens' Black Sea lifeline.

In the wake of Athens' defeat in the Sicilian Expedition in 413, a small Spartan fleet commanded by Chalcideus, who was advised and assisted by Alcibiades, succeeded in bringing a number of critical Ionian cities into revolt from the Athenian Empire. After the revolt of the critical city of Miletus, the Persian satrap Tissaphernes concluded an alliance against Athens with Sparta. The Spartans remained unwilling to challenge the Athenians at sea, and an Athenian fleet succeeded in recapturing several cities and besieging Chios during the later months of 412 BC. In 411 BC, however, further rebellions at Rhodes and Euboea, and the capture of Abydos and Lampsacus on the Hellespont by a Peloponnesian army that had marched there overland, forced the Athenians to disperse their forces to meet these various threats. The Spartan fleet could now move freely in the Aegean, and took advantage of its newfound superiority by lifting the blockade of Chios and bottling up the Athenians' Aegean fleet at Samos.

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