δι' ἐρημίας πολεμίων πορευόμενος → he marched on without finding any enemy, his route lay through a country bare of enemies
ăd-invĕnĭo: vēni, ventum, 4, v. a. ad, intens.,
I to find out, to devise, Vulg. Exod. 35, 33; Dig. 48, 19, 28; cf. also Serv. ad Verg. A. 6, 603: lapicaedinae adinventae sunt, Labi Ins.: si quis ainventus (for adinventus) fuerit hoc fecisse, Mur. Ins. 794.