The central theme of this chapter is the impact of war on the Greek world in the first half of the fourth century B.C. Thucydides described the Peloponnesian War as the greatest disturbance in Greek history, a war that came to affect almost the whole of the Greek world and part of the non-Greek world as well. His verdict was amply verified by subsequent events.

Not every Greek state was affected at once or to the same degree. The central Peloponnese, for example, was largely unscathed, and Elis was in a flourishing condition at the time of the Spartan invasion of c. 402 (Xen. Hell. III.2.21–31). Boeotia as a whole suffered only one abortive Athenian invasion in 424. In the Decelean War the Thebans enriched themselves on the plunder of Attica and acquired many of the runaway Athenian slaves (Hell. Oxy. XVII (XII). 3–5). The impact of the war on the society and economy of the two protagonists differed strikingly. Sparta's victory, and the role she chose to play in Greek affairs after 404, placed strains on her society which she could not withstand. Whereas the fifth-century Athenian empire had spread prosperity through all classes of Athenian society, and thus helped to cement political and social stability, the Spartan empire aggravated internal tensions and inequalities in Sparta. The gap between Sparta's ambitions, and the resources available to her, seemed dangerously wide. Sparta's decline in the fourth century, within little over a generation after her victory, followed as a long-term consequence of that victory.