Part 1/2 of Nod: Washington DC in my Command & Conquer 3: Tiberium Wars – Hard walkthrough.
The key to this level is to be quick, let it drag too long and the superior GDI firepower will push you into a long stalemate. They have Predators after 10-15 minutes, and they will use them against your defenses. 4-6 Laser Turrets in a curve from the north east to the south east of your base should do, back them up with 3-4 Shredders. Other than that, the level is pretty easy. As for attack, solo Flame Tanks will do for all the smaller outposts dotted about, and the Silos, but for the main base (the next part), back them up with some Attack Bikes. In this instance, your Flame Tanks should act as sponges, so your less durable Attack Bikes can destroy their vehicles without too many casualties.