Strong's G4759 — στρατοπεδάρχης (noun)
stratopedarches (strat-op-ed-ar'-khace) n.
1. a ruler of an army
2. (specially), a Praetorian prefect
[from G4760 and G757]
KJV: captain of the guard 
Root(s): G4760, G757 
Hebrew root: ἄρχω