Explain the grammatical construction 'in consiliis capiendis' in "sunt in consiliis capiendis mobiles" (Caesar, De Bello Gallico, IV.5)
The whole phrase is an ablative of manner; it describes the adjective "mobiles" (flexible). They are "mobiles" in regard to "consiliis capiendis" (the act of making plans).
"Capiendis" is a gerundive, a passive verbal adjective, that describes "consiliis." As it is an adjective it agrees in number case and gender with it's complement, "consiliis" (a neuter noun in the ablative plural.)
The whole phrase would be translated "they are flexible when making plans."
FW
Related Latin A Level answers
All answers ▸What is gerundival attraction?
On Aeneas' shield in Book 8, what images does Virgil use to make Octavian special and to elevate him above the status of combatant in a civil war with Antony? How are Octavian's opponents portrayed?
Comment on this section of text (Aeneid XII lines 742-765). How is Turnus portrayed, particularly in light of his imminent final battle?
To what extent is Dido a sympathetic character in Aeneid 4?