This study examines how in the dispute between Thukydides and Hellanikos, scholars have long taken it for granted that the preserved historian was right and the lost one mistaken, despite the fact that the Battle of Oinoe, for example, does not fit into the chronology of Thukydides. By restoring the dates recorded by Hellanikos, Schreiner asserts that a reliable chronology can be established. The first historian to record the period from the Persian Wars to 431 BC was Hellanikos, the author of the lost History of Athens from its mythical origins through the fifth century BC. He reported there was one war between Athens and Sparta from 431 to 421 and another from 412 to 404, and that the first was caused by contemporary events of the 430s. Thukydides, writing a monograph on a war he sought to establish as the most disastrous to date, criticized Hellanikos as chronologically inaccurate and lacking an appreciation of the impact of a stronger Athens. Thukydides asserted that there was only one war, beginning in 431 and ending in 404, caused by the growth of Athens following the Persian Wars and the fear that growth inspired in Sparta. The book, in reviving the text of Hellanikos, should encourage scholars of antiquity and military history to re-evaluate their interpretations of the era.