T. G. Tucker, Commentary on Thucydides: Book 8

ἐς τὴν . . . φιλίαν . . . διαβάλλειν. ἐς gives the ground of the expected disaffection. Cf. v. 75, ἐπιφερομένην αἰτίαν ἐς μαλακίαν; Xen. Anab. ii. 6, 30, μέμφεσθαι εἰς φιλίαν.

ὁ μὲν answered by οἱ δ᾽ ἐκ τῆς Σάμου, c. 89. μὲν implies that Thucydides is about to leave Alcibiades for affairs elsewhere.

τῆς Φασήλιδος καὶ Καύνου Phaselis (in Lycia) is beyond Caunus, some forty miles westward of Aspendus, on the Pamphylian Gulf. It was a town of importance in trade (ii. 69). Thucydides mentions the main destination first (cf. i. 116, ἐπὶ Καύνου καὶ Καρίας), and then adds, as worth mentioning, καὶ Καύνου, as Caunus lay in the way. For similar reversal of order, though without the same reason, cf. iii. 29, προσμείξαντες ἀπ᾽ αὐτῆς (sc. τῆς Δήλου) τῇ Ἰκάρῳ καὶ Μυκόνῳ. In c. 108, § 1, the return voyage is ἀπὸ τῆς Καύνου καὶ Φασήλιδος, where Thucydides looks at the two places in combination and mentions them in order from the western point of view The single article in each case combines the two places into one geographical notion.

ἄνω practically = ‘eastward.’ The part of Asia Minor on the Aegean Sea is called τὰ κάτω, the parts farther east are τὰ ἄνω. The king of Peisia comes down to the Grecian sea, a Greek goes upward into the king's territory by land, or parallel to such direction by way of the king's waters.