Could use some Guidance ?!!!

Hey, so i graduated high school, im currently 26 years old, a warrior at heart willing to fight for self, However want to become a soldier, and now use that fire for serving, i would like to study heavy into engineering to create a basic start for a foundation and later branch into the others such as mechanical, electric, civil, bio, and computer, I know realistically it's pick one and go on with it however, i would like to know theoretically what would be that base, to start such routes, my dream is aerospace engineering.