Part 2 opens with the retreat of the Persians, after Thermopylae and the battle of Salamis. Athens, which had been allied with Sparta against Persia, begins to experience an expanded economy (and democracy under the leadership of Pericles). His construction of the long walls - fortifications which connect Athens to Piraeus - is considered to be a hostile act by an increasingly paranoid Sparta, and is the basis for future discord between the two states. Meanwhile, Spartan marriage customs are discussed, and the differences in the role of women in Sparta and the rest of Greece is studied (Spartan women were relatively "free"). In 464 BC, a massive earthquake near Sparta causes massive disruption, allowing the Helots to revolt. A desperate Sparta asks Athens for help, only to change their minds once it is clear that Athens could side with the Helots. Sparta expels the Athenians, and, eventually, war begins. The surprising surrender of a Spartan detachment on the isle of Sphacteria is a major blow to Sparta's reputation of invincibility.