The Athenians, having in 427 BCE made…
416 BCE
The Athenians, having in 427 BCE made one attempt (under Nicias) on the rebellious, but ostensibly inoffensive island-state of Melos, still wish to round off their Aegean empire irrespective of the Dorian “ancestry” of the Melians.
They try again in 417 BCE, attacking the Melians in reprisal for the islanders' neutrality during the Peloponnesian War.
Why?
First, Melos may have contributed to the Spartan war fund as early as 426 BCE.
Second, Athens had assessed Melos at the exorbitant sum of fifteen talents in the context of the general increase of 425, and because the Melians have not paid up, Athens possibly sees them as recalcitrant subjects.
Third, the fact that some Athenian subject allies join in coercing Melos in 416 BCE demonstrates that Ionians and Aeolians can be mobilized against Dorians and perhaps even that they positively approve of all the implications of a notably ruthless action: Athens slays the island's entire male population. (The historian Thucydides, in his “Melian Dialogue,” preserves the speeches made in negotiations between the Athenians and Melians that preceded the military action.)