Thucydides, an Athenian soldier who later wrote the war, is still telling Athens against Sparta, the two leading cities of Greece, in the late fifth century BC. This is Book 5 of his History of the Peloponnesian War. In Book 4 the fighting should have stopped: Athens trapped full Spartan citizens on an island off the Peloponnese, Sparta asked for peace, Athens wanted more, and Brasidas, a Spartan general, took Amphipolis, Athens’s silver-road city in Thrace.

Book 5 opens with the deaths that make a pause possible. Cleon, the Athenian who pushed the war in the assembly, and Brasidas both die under the walls of Amphipolis. The Peace of Nicias is signed and cheated at once; allies refuse the oaths. Alcibiades, young, rich, and dangerous, knits Argos, Elis, and Mantinea, cities in the Peloponnese, against Sparta. At Mantinea the Spartan line holds and the coalition breaks. Then Melos, a small island that had stayed out of the war. Athenian generals argue power, not justice: the strong do what they can, the weak suffer what they must. The Melians will not yield. The men are killed; the women and children sold. In the Piraeus, Athens’s harbor, people already talk of Sicily.