The Corinthians say the Athenians go after the two birds in the bush, and they get them, because they grab fast. The Spartans delay, due to worrying about losing the bird in hand.
μόνοι γὰρ ἔχουσί τε ὁμοίως καὶ ἐλπίζουσιν ἃ ἂν ἐπινοήσωσι διὰ τὸ ταχεῖαν τὴν ἐπιχείρησιν ποιεῖσθαι ὧν ἂν γνῶσιν.
My translation effort: For they [i.e. the Athenians] alone both hope for and at the same time possess whatever they have in mind, due to speedily performing the attack [ἐπιχείρησιν] on which-things they thought.
Here is my effort at unwinding the grammar:
μόνοι γὰρ ἔχουσί τε ὁμοίως καὶ ἐλπίζουσιν: alone they have and at the same time hope for
ἃ ἂν ἐπινοήσωσι: whatever they may have in mind [ this is a relative noun clause, functioning as direct object of both ἔχουσί and ἐλπίζουσιν]
διὰ τὸ ταχεῖαν . . . ποιεῖσθαι: by swiftly performing [articular infinitive]
τὴν ἐπιχείρησιν: the plan/conception/idea [direct object of articular infinitive]
ὧν ἂν γνῶσιν. of which-things they thought up. Because ὧν is plural, its antecedent must be the ἃ in ἃ ἂν ἐπινοήσωσι. ??
Your grammatical analysis is basically spot on.
A few suggestions, recognizing that there are many ways to translate a Thucydidean sentence like this one.
ἔχουσί τε ὁμοίως καὶ ἐλπίζουσι – τε ὁμοίως καὶ here can be translated “as soon as”: “they possess/acquire as soon as they conceive the hope/desire for.”
ἃ ἂν ἐπινοήσωσι – maybe “whatever they conceive of” or “whatever comes into their mind,” translating loosely.
διὰ τὸ ταχεῖαν τὴν ἐπιχείρησιν ποίεισθαι – maybe “by speedily making the attempt on.” I don’t think ἐπιχείρησιν here is necessarily a military attack. Translating the predicative adjective ταχεῖαν as an adverb, “speedily,” is good.
ὧν ἂν γνῶσιν – this is the construction labeled “incorporation” or sometimes “attraction,” as I think you recognize: the relative pronoun is the object of γνῶσιν, but its genitive case is the case of its understood antecedent in the main clause. τὴν ἐπιχείρησιν . . . τούτων ἃ ἂν γνῶσιν is the underlying structure, but Greek telescopes the pronouns to just ὧν.
γνῶσιν - here perhaps better “determine” or “decide.” And this is a “general” relative clause: “whatever they decide.” The aorist subjunctive is aspectual, not a past tense.
Hope this is helpful. This is a valiant effort on your part. I remember how hard it was to wrestle with this speech and others in Thucydides. There are passages where there are differing interpretations and no consensus.
Your comments are very helpful, and worth studying.
This sentence took about two hours. What finally worked was copying the sentence into a text editor, and then matching phrase-by-phrase the sentence with the Thomas Hobbes translation. This helped me see the sentence as a series of phrases. Hobbes’s translation is the most helpful I’ve seen.
The hardest to see was how “ἔχουσί τε ὁμοίως καὶ ἐλπίζουσιν”
matched with “ἃ ἂν ἐπινοήσωσι”.
I am beginning to think that in these speeches Thucydides writes with a speaker in mind, one using facial expression, dramatic pauses, tone of voice, and gestures to fill out the meaning of the text.