E.C. Marchant, Commentary on Thucydides: Book 6

μαρτύριον—sc. ὡς εἰκότως ἄρχομεν. It is necessary for us, as hereditary enemies of the Dorians, to secure ourselves.

ἔχει δὲ καὶ οὕτως—‘moreover the case stands exactly as follows.’ Classen and others explain this οὕτως as referring to what precedes, which is further dealt with in what follows. But the δέ forms an antithesis to what precedes. The general principle, says the speaker, is enough to justify us; but there is besides the following special circumstance. οὕτως ἔχειν often refers to what follows.

Ἴωνες ὄντες Πελοποννησίοις—‘being Ionians in the eyes of the P., while they were Dorians and superior in numbers and near neighbours of ours.’ In § 2 he has said οί Ἴωνες πολέμιοι τοῖς Δωριεῦσίν εἰσιν. So now, instead of saying πολέμιοι ὄντες Πελοποννησίοις, he ingeniously says Ἴωνες (=πολέμιοι) ὄντες Πελοποννησίοις. (The edd. have, I believe, missed the meaning of this sentence. For the alterations of the text see the crit. note. The old explanation, that αὐτῶν is a repetition of Πελοποννησίοις in a different case by anacoluthon, is quite untenable. Herbst believes there is an ellipse of πολέμιοι, but I do not see the need of this.) This sentence admirably expresses the contempt of the Dorians for the Ionians (cf. c. 68), who were only fit in their view to be their subjects.