In the battle of Athenians against Spartans in the Peloponnesian War in 425 BC, the Spartans were based on Sphacteria. The Athenians landed on the island and slaughtered the Spartans. 292 Spartans survived ans surrendered. They could defend the island for 72 days.
Centuries later, in the War of Independence in 1825, 350 Greeks got killed here on Sphacteria during one of the biggest massacres of that war.