Exegesis:

hotan de idēte kukloumenēn hupo stratopedōn Ierousalēm ‘but when you see Jerusalem being surrounded by armies.’

kukloō ‘to surround,’ ‘to encircle.’ Note the present tense: the encircling is not yet completed, otherwise some of the following injunctions would be pointless.

stratopedon ‘army camp,’ hence ‘army,’ ‘army corps,’ ‘legion.’

tote gnōte ‘then you must know,’ referring to a future time.

hoti ēggiken hē erēmōsis autēs ‘that the time of her devastation has drawn near.’ For ēggiken cf. on v. 8.

erēmōsis ‘devastation,’ ‘desolation.’

Translation:

Jerusalem surrounded by armies, or, ‘that armies are engaged in surrounding J., or, on the point of surrounding J.’ Armies, or, ‘(troops of) soldiers’; if the word for ‘to surround’ does not clearly express the hostile intention, one may have to say ‘enemy armies.’

Then know, i.e. “then you may be sure” (New English Bible), ‘you must realize then’ (cf. Bible de Jérusalem).

That its desolation has come near, or, ‘that the time for it to fall desolate has come near’ (Marathi), ‘that the hour has come for it to be destroyed’ (Tzeltal), ‘that it is about to be destroyed (cf. Ekari, Shona 1963), or, will soon perish/fall/go-to-ruin,’ ‘that far-off not, they will destroy it’ (Kituba).

Quoted with permission from Reiling, J. and Swellengrebel, J.L. A Handbook on the Gospel of Luke. (UBS Handbook Series). New York: UBS, 1971. For this and other handbooks for translators see here . Make sure to also consult the Handbook on the Gospel of Mark for parallel or similar verses.