E.C. Marchant, Commentary on Thucydides Book 1

2. δυναμένους—Stahl takes this and ὄντας in apposition to Κορινθίους, and removes the second καί so that only προκαταλαμβάνοντας depends on αἰσθάνεται. It is better with Steup to render the first καί both, and to make ὄντας also depend on αἰσθάνεται: ‘and are preparing by trying to subdue us for an attack on you.’

5. κατ: αὐτοὺς ... στῶμεν—confront them.

δυοῖν φθάσαι ἁμάρτωσιν—(1) ‘may not lose two things’ means may secure one or the other: hence ἢ ... ἤ following. (2) But the construction of φθάσαι and δυοῖν is doubtful. Taking δυοῖν dependent on ἁμάρτωσιν, as in Andoc. 1.20 δυοῖν τοῖν μεγίστοιν κακοῖν οὐκ ἦν αὐτῷ ἁμαρτεῖν, most cdd. make φθάσαι epexegetic, to gain them before (we make alliance). The order is against this, and φθάσαι should then=to gain one of them. It has been proposed to remove φθάσαι; but it is best, with Croiset, to take δυοῖν as dat.=‘fail to be beforehand with two things.’ Either they will inflict a disastrous defeat on Corcyra, or frighten her into joining themselves.