Dative of Military Accompaniment.—The dative is used in the description of military movements to denote the accompaniment (troops, ships, etc.) of a leader:
ἐξελαύνει τῷ στρατεύματι παντί
a. An extension of this usage occurs when the persons in the dative are essentially the same as the persons forming the subject (distributive use):
ἡμῖν ἐφείποντο οἱ πολέμιοι καὶ ἱππικῷ καὶ πελταστικῷ
b. The dative of military accompaniment is often equivalent to a dative of means when the verb does not denote the leadership of a general.
Herbert Weir Smyth [n.d.], A Greek Grammar for Colleges; Machine readable text [info] [word count] [Smyth].