''Field Commander'' help

I'm on the mission where you're trying to intercept the Wolf leader before he escapes the board... you start on the bottom of the map with one rocket launcher and one grunt already made, as well as a sub and a battleship. There are shallow waters which slow you down, and time after time when I fail the Narrator says ''If you build a rocket launcher, you can bombard them from the shore as they go by...'' Well, I've gotten a rocket launcher to the north-most atol (island), and it doesn't seem to help.The problem is they've got tremendous naval strength built up already and it's a matter of you crossing the map in time to destroy the enemie's transport before it gets away...If you know the scena mining and other matters slow you tremendously. I've tried different squads and stuff, none of it is working If you know what I'm talking about and can help me out, I'd be appreciative. This one level has me stuck.