E.C. Marchant, Commentary on Thucydides Book 1

[2] γάρ—as ‘the movement’ meant by κίνησις must be (1) the war itself, and (2) the unrest that preceded it, γάρ cannot introduce the reason of the expectation that the war would be important, but must be epexegetic.

12. μέρει τινί—a considerable part, as, for example, Thrace and Macedon. Supply ἐγένετο, affected.

ὡς δὲ εἰπεῖν—qualifying πλεῖστον. Note that ὡς（ἔπος）εἰπεῖν never apologises for a metaphor, but always limits a sweeping or universal statement. Hence (it extended, ἐγένετο), one might almost say, over the greatest part of mankind; i.e. it affected perhaps a greater part of mankind than had been affected by any previous commotion. Of course the possible exception is the Persian wars.

(Whatever be the exact construction of μεγίστη δὴ ... ἀνθρώπων—and the words are variously interpreted—Thuc. over-estimates the importance of the war. If we supply μεγίστη δὴ ἐγένετο to μέρει τινί and ἐπὶ πλεῖστον, the exaggeration is extreme. ἐπὶ πλεῖστον is taken by Classen and others to mean the greatest part of the (known) world; but this involves a very great exaggeration of a fact ascertainable; and it is unlikely that Thuc. would make such a sweeping statement. It looks also as if πλεῖστον, more than before, were meant to be parallel to μεγίστη, greater than before. The text has no appearance of being corrupt or interpolated.)

13. τὰ πρὸ αὐτῶν—the events that preceded this disturbance (κίνησις). The neut. αὐτά is frequently used by Thuc. with reference to the details of the subject he is dealing with.

(This phrase cannot refer to events that immediately preceded the war; for (a) διὰ χρόνου πλῆθος would then be absurd, (b) Thuc. himself gives an account of the fifty years preceding the war as a period well known, (c) the Persian wars could not be ineluded in οὐ μεγάλα νομίζω γενέσθαι κατὰ τοὺς πολέμους (cf. c. 18. 2). Thuc. must be thinking of the period of the Trojan war and of that between the Trojan war and the Persian war, i.e. to the end of the Tyrants. But the words are very inexact; cf. Intr. p. xx).