The Peloponnesian War broke out in 431 BC and continued intermittently for twenty-seven years. It pitted an all-powerful land force (Sparta and its allies) against a supremely powerful naval force (Athens). Thucydides actually participated in this conflict, a war which he realized would have a greater influence on the history of Greece than any other war. The History of the Peloponnesian War is true to its title: it is a story of battles and sieges, of alliances hastily made and soon broken, and most importantly, of the behavior of people as the war dragged on and on, and the inevitable "corrosion of the human spirit."
Translated by Richard Crawley