marines are a specific branch of the army
no, the marines are their own branch of the us military.

This scene irks me for a different reason. It shows up like 20 or 30 minutes into the movie, and the ship has every protagonist introduced so far inside it. No loving way is something bad going to happen to them. All that fancy CGI means nothing if there was never any actual risk involved. And I thought the CGI was great! New Star Wars CGI is loving beautiful. The big ship battles in Rogue One were suspenseful and exciting because it wasn't clear what was going to happen -- you knew how this story ended, the plans are sent, but how this battle will go is up in the air. In this clip, not only is the outcome immediately clear (The good guys don't die and the iconic ship doesn't blow up!) but there's no suspense. It's like the whole scene was created for advertisements, which I dunno, maybe it was.
also... big fight,