I also tend to think of stormtroopers in a WWII context. (While not quite of GRRM's vintage, there were plenty of war films about when I was growing up.)
I suppose the designation was used, in fiction/films, as a shorthand: one knows which side a stormtrooper is on (in the same way as one knows that a "guard" is German in Stalag-whatever) whereas a soldier may have to be further categorised.
I suppose the designation was used, in fiction/films, as a shorthand: one knows which side a stormtrooper is on (in the same way as one knows that a "guard" is German in Stalag-whatever) whereas a soldier may have to be further categorised.