Who do you plan to combat? Not really very many magick wars going on these days. We have to keep as many of us around as possible =)
Astrally you can sometimes come into confrontation. But if you don't astrally project, it has no purpose.
Unless you can see and hear spirits and plan to be a real "Ghostbuster", combat magick has no purpose on the physical plane.
I know combat magick, and I've fought astrally when someone attacks me. Its also helpful when deflecting magick shot at you with a dirty look etc. But it isn't necessary to learn. Its easy to avoid confrontation, I just have a pride/honor issue and don't stand down to a fight. I think it's a Chicagoan thing....lol!