As explained in the Preface to Hornblower's edition of bk. 5 (2013), most of the sections of the Introduction to that volume covered bks. 5 and 6 together. The Introduction to the present volume does not, therefore, revisit every aspect of every topic covered there. The promises there made, about postponement of certain topics – Herodotus on Kleomenes, Aigina, and Homer – until the Introduction to bk. 6, have been kept, but not by the straightforward inclusion of entire sections with those titles. We have nowhere attempted a separate section on Herodotus’ sources for bks. 5 and 6. More than a century ago, Felix Jacoby (1913: cols. 419–67 [1956: 114–38]) heroically went through the whole of the Histories, assigning sections to sources. The trouble with this sort of operation, certainly unfashionable in 2016, is that some such suggestions are much more plausible than others, so that the question is best dealt with in notes to individual passages.
Brevity has been at a premium throughout. We particularly regret that our references to modern scholarship have often had to be perfunctory, giving the impression of much more originality than we can claim.
As in bk. 5, we use bold type, for clarity and brevity, when referring to chapter numbers of the book which is the actual subject of our commentary; thus 70.2n. = ‘see note on 6.70.2’. For references to Hornblower's 2013 commentary on bk. 5, we have said e.g. ‘see 5.126.1n.’, because we regard bks. 5 and 6, and therefore also the commentaries on them, as a continuum. For the most part we follow Herodotus’ own spelling of personal names and place names, but we apologise for inconsistency; in particular we could not, as children of the 1960s, bring ourselves to talk about Hippies when discussing the Peisistratid tyrant.
We acknowledge gratefully the insights provided by the contributors to two Oxford seminar series: a graduate class on bk. 6 in 2011, and a seminar series on the ‘green and yellow Herodotus’ in 2013, covering all nine books, and addressed by the editors of individual volumes. Hornblower would also like to repeat his 2013 thanks to those UCL MA students who attended his two-term class on bks. 5 and 6 in 2009–10.