The bulk update request #4449 is pending approval.

create alias army_helmet (95) -> military_helmet (207)
create alias soldier_helmet (19) -> military_helmet (207)
create implication military_helmet (207) -> combat_helmet (172)

Reason: Same thing. Different words.
Military helmets are a type of combat helmet.
The military helmet tag has been used to refer to combat helmets worn by modern day soldiers.