The Peloponnesian War (431-404 b.c.e.) was the greatest "disturbance" in Greek history to that time. The bitter rivalry between the two chief city-states, Athens and Sparta, and their respective allies ended with the ruin of Athens' naval hegemony and what the Greek historian Thucydides (ca. 460-400 b.c.e.) called a "convulsion" affecting all humankind. Thucydides recreates the often savage events of the war and brings to life its chief protagonists: Pericles, Nicias, Cleon, Alcibiades, and others. The first of the "scientific" historians, Thucydides makes use of documentary material and relies on eyewitness accounts; even where direct documentary evidence is lacking, his keen understanding of human nature helps him to uncover the truth of what actually happened.