Usage: 2 forms in 2 verses
Form Translated As     In Verse(s)
οπλόμαχοι his armed warriors LXX.Isa.13.5
οπλομάχω of armed warriors LXX.Isa.13.4

Liddell-Scott-Jones

ὁπλομάχος (hoplomachos) an armed warrior G:N-M

ὁπλομάχος-μάχος [], ον,

fighting in heavy arms, [LXX+5th c.BC+]

__II substantive ., , one who teaches the use of arms, drillsergeant, opposed to amere fencing-master, [Refs 4th c.BC+]

LSJ Scripture Refs: LXX.Isa.13.5