There a many NSA personnel died while carrying out their mission, according to Inside NSA documentary lah.

Desert maybe can lar, have mbt running around blowing things up
In the tropics would be plain suicide, you never know atgm/rpg would pop up behind random bushes

Deswai US with armor superiority in vietnam would still need infantry to clear the way first, the japanese too learnt this hard way encountering british qf guns on the malayan roads

They started as signal intelligent, mostly cryptographers. Some missions need to be closed to conflict zone to be effective like flying on spy plane etc. I think one of their biggest single event casualty was the attack by IDF on their sigint ship (USS Liberty?) off Israel during six-day war.

Dat because it yet to hit their back yard.
anyway dat also what would happened when you put someone without any military background as menhan.