εἰ γὰρ δὴ μέματον Τρώων καταδῦναι ὅμιλον
We also find this use of καταδύω to mean ‘go behind enemy lines’ in an ambush theme at Odyssey 4.246: ἀνδρῶν δυσμενέων κατέδυ πόλιν εὐρυάγυιαν, and again at 4.249. (Athena’s action at Iliad 4.86 seems to have a similar flavor, but Apollo also “sinks into” the crowd of Trojans below at 10.517, and the Trojans are not his enemy, so the verb seems to specify gods visiting mortals in those cases.) It is also used to mean ‘enter’ battle (Iliad 3.241 and 18.134).