Only one choice again. The Harkonnen have taken the Fremen hostage and you have to take over a starport, and then take over the Harkonnen barracks. Warning here I learned the hard way - if you take your time, their forces become unstoppable! It reminded me of a certain Dungeon Keeper level with the same problem. The trick is to move quickly.

First, send all of your forces straight up the right hand side to grab the starport. It's essentially right over you and pretty easy to attack. Buy another harvester, a carryall, and as many other tanks and armor that you can. Use the MCV to set up a new base right above the starport. Start building windtraps and turrets to protect your lower base. When the reinforcements arrive, go straight north from this base. There's a small island up there.