E.C. Marchant, Commentary on Thucydides Book 1

κατ᾽ ὀλιγαρχίαν κτλ.—i.e. θεραπεύοντες δὲ ὅπως πολιτεύσουσι κατ᾽-ὀλιγαρχίαν（κατά of mannei), ἐπιτηδείως σφίσιν αὐτοῖς μόνον (‘in their, the Lacedaemonian, interests alone’). Cf. Arist. Pol. 4.11 τῶν ἑν ἠγεμονίᾳ γενομένων τῆς Ἑλλάδος ... οἱ μὲν δημοκρατίας καθίστασαν, οἱ δ᾽ ὀλιγαρχίας, οὐ πρὸς τὸ τῶν πόλεων συμφέρον σκοποῦντες ἀλλὰ πρὸς τὸ σφέτερον αὐτῶν.

13. ναῦς τε τῶν πόλεων—having gradually taken over (assumed possession of) the ships of the various cities. Cf. c. 99. 3.

16. καὶ ἐγένετο αὐτοῖς—two widely different views are taken of this passage according as αὐτοῖς means (a) ‘the Athenians’ only or (b) ‘the Athenians and Lacedaemonians.’ Omitting minor differences, we get (a) ‘and so her own resources for carrying on this war reached a greater strength than (what she had) when she stood at the height of her prosperity side by side with the undamaged forces of her confederates’; i.e. Athens had appropriated the forces of her confederates, as it were, and thus was stronger than when she was at the head of a body of independent allies. (b) The forces of Athens and Sparta separately were stronger than they had been (both together) during the period of the ὁμαιχμία (Classen) or ‘stronger than the strongest power each separately had wielded with its still undamaged συμμαχία’ (Herbst). (a) accords with what Thuc afterwards says of the growth of Athenian power (cf. c. 118) By τὰ κράτιστα he means the time before the reduction of Naxos (466 B.C.). ξυμμαχία ἀκραιφνής is in contrast with the appropriation of ships and imposition of tribute. (b) with Classen's rendering is too strong; with Herbst, we certainly hardly feel the statement, as far as it refers to Sparta, consistent with the reference to her policy made above.

20. τὰ παλαιά—this, as Herbst and Steup point out, refers only to the time before the expulsion of the tyrants—see note on c. 1.2 τὰ γὰρ πρὸ αὐτῶν κτλ. The events of the Persian wars were fully known, and in c. 18. 1 Thuc. comes to them as to modern events. Therefore we must suppose cc. 18 and 19 to form a long parenthesis—see the analysis of the προοίμιον, Intr III. note.