ὄπισθεν δὲ ἡ φάλαγξ ἐφεπομένη, εἴ τι τῶν σκευοφόρων ὑπολείποιτο, οἱ προστυγχάνοντες τῶν ἀρχόντων ἐπεμέλοντο ὡς μὴ κωλύοιντο πορεύεσθαι.
ἡ φάλαγξ ἐφεπομένη, is I am sure nom pendens but I dont know how to understand it.
It’s a simple anacoluthon, as he drops the phalanx itself as the subject of the sentence and switches to the officers who took care of any stragglers in the baggage-train in front. The switch is mediated by the intervening if-clause. The writing is a bit sloppy but not at all difficult to follow.