The Melian Dialogue, more precisely the dialogue between the Athenians and the Melians, is a debate included by Thucydides in his History of the Peloponnesian War, an account of the disastrous conflict that for 27 years (431-404) opposed the powerful Greek cities Athens and Sparta. The Melian Dialogue takes place in the fifteenth year of the war, during the confrontation in 416-415 between the Athenians and the people of Melos, a small island located in the southern Aegean Sea, east of Sparta. The Athenians require that the Melians submit and pay a tribute, under penalty of seeing their city destroyed. The Melians asserted their right to remain neutral, appealing to the Athenians' sense of justice and their compassion towards a small, peaceful and defenseless city. The Athenians answer curtly that justice does not apply between unequal powers, and put the siege in front of Mélos as they had threatened to do it; having starved the city and obtained after several months its surrender, they kill the men in age to fight and reduce to slavery the women and the children.
Neither side was blameless in the Peloponnesus war. It was humanity at its absolute worst. Victor Davis Hanson has a great book titled ‘A War Like no Other’ about it.