ἓν ἔτι . . . ὥστε—i.e. ‘if they only succeed in gaining over the Italian citres’; the ὥστε clause being epexegetic of ἓν. Cf. Herod. V. 31 εἰ γὰρ τοῦτό γε δοκέει ὑμῖν εἶναι χρηστὸν ὥστε τυραννεύεσθαι τὰς πόλις; Theocr. 14, 58 εἰ δ᾽ οὕτως ἄρα τοι δοκεῖ ὥστ᾽ ἀποδαμεῖν.
τῆς Ἰταλίας—already before the Peloponnesian war both the Athenians and Spartans had made alliances in Italy, by which they understood only the S.W. corner of Italy, from Heraclea on the east and the Laus on the west.
ὁρῶντα . . . ἐπιβοηθούντων—cf. II. 25 ὄντι ἀσθενεῖ καὶ ἀνθρώπων οὐκ ἐνόντων.
διαπεπολεμήσεται—they will bring the war to an end without striking a blow.