When I was in the Army is was used degrogatorially about those who were extremely military-minded -- "A gung-ho son of a bitch" or "Don't be so damned gung-ho." It was NOT used in the original sense!

I think it would fair to say that here in the UK, it does tend to be used in this fashion. More the idea that certain military elites believe themselves to be able, or convey to others that they can 'walk-on-water'.