Thomas Arnold (1795-1842) published Volume 1 of his edition of Thucydides' History of the Peloponnesian War in 1830. It contains the first three books of the History, covering the causes of the war (which began in 431 B.C.E.), and continuing up to the Athenian purification of Delos in 425 B.C.E. The text and apparatus closely follow Bekker's 1821 critical edition. However, Arnold freshly collated a number of Greek manuscripts, including the important tenth-century Laurentian manuscript C for Book 3, which led to some revision of Bekker's text. Arnold's major contribution to Thucydidean scholarship lies in the detailed topographical and historical notes accompanying the text, which explain its geographical and political background. For many generations Arnold's work has provided an indispensable guide through the complex geo-political context of the History, enabling students to appreciate its narrative, language and place in historiography.