[@IceHeart]

Oh, I think I know where the confusion started from.

The five marines are above the main entrance of the base, standing on the roof. They are hiding behind a small wall, it's height only reaching up to someone's waist. So they're basicly crouching behind it. There is a cannon on the left of the small wall, and one on the right. 

Sorry, I didn't describe that bit very well.

Also, waiting on posts guys :P