καὶ ὑμῖν . . ἰδίᾳ—as distinct from their services to the common cause.
ὅτεπερ δή—‘at the very time when,’ in 464 B.C.
τῶν . . ἀποστάντων depends on φόβος. For the position of the attrib. partic., not rare in Thuc. when other qualifying words are added, cf. II. 18 ἡ ἐν Ἰσθμῷ ἐπιμόνη γενομἐνη, c. 67, 3.