In 479 B.C., soldiers from city-states throughout Greece united to put down a common enemy, the invading army of the powerful Persian empire. That military venture heralded a new age of cooperation among rivals, and in Athens, it secured the continuation of democracy while ushering in a golden age of art, architecture, literature, science, and philosophy. It wouldn't last. Ignited by seemingly insignificant civil conflicts in distant territories and spurred on by the interests of third-party cities, the Peloponnesian War began in 431, pitting Athens against its old rival Sparta in a conflict that would stretch across 27 years and leave both powers greatly diminished. As Donald Kagan points out in The Peloponnesian War, the conflict was marked by plague, unexpected reversals of fortune, badly miscalculated military ventures, the rise and fall of charismatic politicians, and ends-justify-the-means atrocities committed by both sides on a scale never before reported in history. A Yale classics professor, Kagan previously authored a history of the war in four volumes, each dedicated to a distinct phase of progress through full-scale conflict, fleeting peace, and back to war again. This chunky single volume boils the series down for the general reader without seeming to simplify the subject. Kagan admits it's difficult to follow Thucydides' contemporary history, which is still the primary source for scholars today, though it cuts off before the end of the war and shows unabashed prejudice for the Athenians. (Kagan seems to have a rooting interest in that side, too, but it's hard not to prefer Aeschylus and sculpture to black pudding and rough bedding.) But even without the problems in Thucydides' version, Kagan justifies his own. Over the course of 500 pages, he gracefully juggles military history, political analysis, and biographical portraiture, fleshing out a war that began with a plague and ended with a tyrannical victory so short-lived that it hardly qualified as a victory at all. Throughout, he refrains from drawing parallels between his subject and future wars, but they're there for anyone who looks. The echoes of Athens' perilous rush to empire and the seemingly minor internal squabbles that explode onto the international scene continue today, as do the lessons of military hubris and Kagan's dreary but difficult-to-refute conclusion that the highest ideals mean little without the military might to keep them alive. As Kagan's account progresses, the low hum of tragedy starts to drown out the glory of this victory or the other, and in the muddle of war, one truth becomes clear: There's no such thing as ancient history.