Seth attempted to deploy you in an attempt to attack the Pentagon, an obvious suicide mission. Because of this, he has diverted necessary troops needed for you to advance into Zaire.
This layout is available if you click the right arrow in the mission selection screen. This layout has an easier start, but the base has a single-entrance chokepoint.
You start at the bottom of the map with six minigunners and four rocket soldiers. Advance your minigunners first to eliminate the infantry, and use the rocket solders to attack the tank. When you reach the base in the south-east, you will have to sell your construction yard to build two engineers.
YOu should receive an transport helicopter, where you can start sending minigunners to the small GDI base. GDI surrounds this base, but the enemies are isolated and can be picked off one by one. Send two enginers on the second transport run, capturing the MCV and refinery (when the harvester is depositing tiberium.)
The map is mostly plain - the only places of interest are tiberium fields, and the main GDI base in the north-east.
When attacking the base, blast through the concrete wall to the right of the entrance. This allows you to target the power stations without having to get close to the advanced guard tower. Once the power plants are down, you can take care of the rest of the base without difficulty.
Before you destroy the helipads, you should remember to get the crate.
This layout is available if you click the left arrow in the mission selection screen. This one gives a more difficult start, although the base has two available routes.
You start at the top of the map with six minigunners and four rocket soliders. Advance your minigunners first to eliminate the infantry, and use the rocket solders to attack the tank. When you reach the base in the north-east, you will have to sell your construction yard to build two engineers.
The next part will be a rough start, as there's plenty of GDI infantry surrounding the base to the south Try to hold out by transporting five minigunners first, then bring two enginners on the second trip. Wait for the harvester to return before capturing the refinery. Remember that if you keep at least one unit to the north, you will distract the A-10 airstrikes - making up for the lack of suitable anti-air.
To the west of the captured base are a few passages to the main base, with four places where a medium tank watches over the canyon. Despite being fortified, you can bring in an APC filled with engineers, and drive to the left just before the concrete wall to caputre six tiberium silos (providing a strong resource boost), but only a tight area for an advance base near the enemy.
If you try to head south, you will need a combination of tanks and rocket soldiers. The tanks can engage the two gunboats that travel back and forth, while the rocket soldiers can shoot down the orcas when they make their attack run. Otherwise, this side of the base is lightly defended, giving a route to the power plants. Remember to collect the crate, as it is necessary for a superweapon later in the campaign.
Once you eliminate all enemy units, the mission should finish. If not, try looking for GDI units parking themselves near the northern shore.