Blow up that really BIG gun turret (Shore Defense Cannon or whatever it's called) BEFORE destroying the SAMs.

If you destroy the SAMs, a helicopter comes in, bombs the turret, and it doesn't count for the objective.

In my opinion, it makes no sense...
Why the hell let Havoc risk his life and waste TONS of C4 on that turret (I remember, I tried to take it down, planted one charge on it and it almost did no damage at all) if a helicopter can do it easier and without risking anything (since the SAMs are down) ?

But anyway, that's the objective...