I’m struggling to understand the grammatical character of ὡς in this sentence. I understand what it says here, but I can’t figure out which category in chapter 57 “Overview of the uses of ὡς” in the Cambridge Grammar describes its usage in this sentence.
I don’t have access to the Cambridge Grammar, but Smyth 1086 says this about ὡς + superlative, with or without a form of δύναμαι:
1086.Strengthened Forms.—The superlative may be strengthened by prefixing ὅτι or ὡς, rarely ᾗ (also ὅσον or ὅπως in poetry): ὅτιπλεῖστοι as many men as possible, ὅτιτάχιστα as quickly as possible, ““ᾗἄριστον” the very best way” [X. C. 7.5.82] (ὅπωςἄριστα[A. Ag. 600]). ὅτι or ὥς is always added when a preposition precedes the superlative: ““ὡςεἰςστενώτατον” into as narrow compass as possible” [X. O. 18.8]. ὡς and ὅτι may be used together: ““ὡςὅτιβέλτιστονἐμέγενέσθαι” for me to become as good as may be” [P. S. 218d].
Thanks that’s helpful – I missed taking note of the superlative. I was aware of how ὅτι can strengthen a superlative as I had already seen that in X. An. 1.1.6 and 1.1.11 but I didn’t know ὡς could do the same, plus the intervening ἂν δύνηται in the construction made it difficult to see what was goiing on. But the Smyth section you posted gives just such a construction!
ἱππέας ὡς ἂν δύνηται πλείστους is a normal sort of phrasing, like the διηγήσομαι passage cited by Sm.1086 (Dem.17.3 as well as Isoc.21.2), cf. e.g. Pl.Rep.367b.
We can best make sense of the construction if we think of ὡς ἂν δύνηται
as an ordinary indefinite adverbial relative clause (Smyth 1768) then qualified by the superlative adverb or adjective. And that will explain why ὡς not ὅτι.