Thucydides, an Athenian later sent into exile, wrote the history of Athens against Sparta from 431 to 404 BCE. This is Book 2. Book 1 set Spartan fear of Athenian growth as the cause and showed both sides voting for war. Pericles planned to sit behind walls and live off the sea.

In 431 the Thebans try by night to seize Plataea, an Athenian ally in Boeotia north of Athens, and fail. Archidamus, a Spartan king, invades Attica, the land around Athens; country people crowd behind the Long Walls to the port, Piraeus. Pericles buries the first year's dead and calls Athens open, daring, a school of Greece. Then plague comes in at Piraeus and law goes. Thucydides catches it and lives to describe the symptoms. Pericles, hounded by the assembly, speaks again for the empire and dies of the fever. Cleon, a popular speaker, is waiting. The Spartans ravage the farms and go home for the harvest. The city fights on without him.