Mar Sara Missions

Mar Sara Mastery achievement is quite easy to get, the only one that presents any difficulty is the Zero Hour mission's The Best Defense... achievement.

On Liberation Day there is not much you need to do except making sure you find and kill all enemy units and take care not to let any civilians die, basically you can save before you run up the last part of the map where all the civilians are so you can redo it if anyone dies.

In the outlaws mission you just need to be fast; pump out lots of SCV's to get your economy going and build two barracks, one with tech-lab for medics and the other one you can exclusively get marines. There is actually not much you can do to make this easier except you massing out marines and work on your micro skills.

It is in Zero hour you will encounter problems; the mission in its own isn't that hard and I could even do it quite easily on brutal difficulty, but killing hatcheries for the "The Best Defense..." achievement is problematic, especially if you want to do "Hold the Line" as well. I Recommend doing the two achievements separately. For hold the line you just need to keep SCV's repairing, it shouldn't be very troublesome if you do it on normal.

For "The Best Defense..." you might get into more problem, the trick is to mass up marines; first you salvage second line bunkers then you will need at least three barracks, one with tech-lab and the others with reactor, build the barracks when you can afford to build and still produce with all your facilities (barracks and command center). Keep producing SCV's at all times and train marines and medics at all times you can afford. You also want both the weapon and armor upgrades before you push out. At about 13-12 minutes left you should push out through the western choke and move north, kill anything that gets in your way and head to the northern camp, there you can kill a few buildings and two hatcheries. After you kill the TWO hatcheries you fall back and hide in the northwestern corner to await your reinforcements. Produce as many marines and medics you can muster over the next 30-120 seconds and then push out with your second force to join your first, by the time you get together the two hatcheries will have been rebuilt and you can kill them again, getting all your four kills from only two hatcheries. Fall back and defend your base for the last few waves of enemies.