Final answer:
During the Peloponnesian War, the Athenians demanded that the Melians surrender or face extermination.
Step-by-step explanation:
The Peloponnesian War was a protracted conflict fought between two powerful Greek city-states, Athens and Sparta, along with their respective allies, in the 5th century BCE. The war lasted for nearly three decades, from 431 BCE to 404 BCE, and had a profound impact on the Greek world, leading to significant political, economic, and social changes. In 415 BCE, the Athenians demanded that the Melians surrender and submit or face extermination during the Peloponnesian War.