κρατησάντων γὰρ—the διήγησις (narratio). (This excellently illustrates Aristot. Aristot. Rh. 3.16.11 ἐν δὲ δημηγορίᾳ ἥκιστα διήγησίς ἐστιν, ὅτι περὶ τῶν μελλόντων οὐθεὶς διηγεῖται ἀλλ᾽ ἐάν περ διήγησις ᾖ, τῶν γενομένων ἔσται, ἵν᾽ άναμνησθέντες ἐκείνων βέλτιον βουλεύσωνται περὶ τῶν ὕστερον.)
μάχαις ταῖς πλείοσι—why this order? to emphasize the adjective. Cf. II. 2.2 ἄνδρας τοὺς ὑπεναντίους.
Συρακοσίους—Classen notes on I. 108 that Thuc. constructs κρατεῖν with accus. when it is connected with μάχῃ or μαχόμενος (or when one of them is clearly imphed in context); otherwise with gen. This rule is generally observed, for κρατεῖν with gen.=κρείσσων γενέσθαι. Cf. Dem. 8.32 ὃν κρατήσαντας τοῖς ὅπλοις; Dem. 19.319 Φωκέας ἐκράτησε (sc. μάχῃ). [Demosth.] 13.17 ἐν τοῖς ὅπλοις κρατεῖν τῶν ἐχθρῶν is bad.
ἐφ᾽ οὓς ἐπέμφθημεν—this remark is mtended as a defence, by reminding the Athenians of the original plan of campaign. Hence ἐπέμφθημεν, not ἐστρατευσαμεν.
ἔκ τε . . . καὶ ἀπὸ—one of the commonest interchanges of prepositions, esp. in Isocrates. In some uses ἐκ and ἀπὸ are different; e.g. of descent, ἐκ is used of direct, ἀπὸ of indirect descent. Even as used here, ἐκ generally expresses the more important or immediate cause.
ἔστιν ὧν—in the nom. plur. always εἰσὶν (οἳ, αἳ); in oblique cases always ἔστιν (ὧν, οἶς, etc) in Thuc., except when words intervene, as in c. 25 ἧσαν τῶν σταυρῶν οὕς.
νικᾶται . . . ἀνεχωρήσαμεν—for the hist. pres. followed by aor., cf. on c. 3.4. (Notice the extreme simplicity and beauty of the style here.)
τῇ δ᾽ ὑστεραίᾳ—sc. μάχῃ, as in III. 91. In I. 44.1 ἐν τῇ ὑστεραίᾳ = in the next day's assembly; and so in v. 46.1. But when no noun precedes, ἡμέρα is meant.
ἀκοντισταῖς βιασθέντες—in c. 43 βιασθέντες ὑπ᾽ αὐτῶν The dat. is not ‘agent,’ but that used in military and naval phrases, of the general's παρασκευή. Hence ὑπ᾽ αὐτοῦ is to be supplied. Note also that with βιάζομαι and all verbs denoting force, ὑπὸ and gen. is common with non-personal agents, as βιασθεὶς ὑπὸ τῆς νόσου. See on c. 13.2.