Quickly rush down to the south and start up your base. As you're moving down south, be sure to check out the first stairs on your right and check out that area to find the 5th Black Box. Use the Scorpion Tank to hold up the enemies while your other units fall back. Head for the base area and quickly garrison any Marines at the Crashed Pelican Garrisonable Center (which gives them better protection). Quickly set up two Reactors, a Barracks, two Supply Pads, Air Pad, Vehicle Depot and four Turrets.