I tried these tactics and they seem to work out really well. Yet please note that they were used in the map "Under" (I only have the demo) and all the games were around 2-10 players.GDI TACTICS FOR "UNDER"
As GDI, you're window of opportunity is somewhat small against Nod. But it is possible to take them out.
TACTIC I
As a mammoth, MRLS, or medium tank, you can always stay a little out of the Nod obelisk's range. There will be one turret that gets in your way, but you can destroy it. There is a mountain near the Nod entrance, and if you stick somewhat behind where it curves, you'll be out of the obelisk's range. From there you can get that turret mentioned previously, and the Nod airstrip, which should cripple them majorly.
TACTIC II
Get a good long-range weapon character such as Gunner or Sydney. When you've done that, go through the tunnel leading into the Nod base (you might want to bring an escort if things get sticky). From there, go to the tunnel exit that's right next to the power plant and obelisk. Equip your weapon and while standing in the doorway as not to get shot by the obelisk, unload your weapon on the power plant. It will take two trips, but if it goes smoothly, you can knock out the base power and the obelsik will be inoperable. Another tactic you could use from there if the base is not defended is to run like crazy after you've unloaded on the power plant and put a C4 on its MCT.
TACTIC III
Once you've accomplished these things, rally up a tank force and destroy the barracks or go in secretly and plant the ion cannon beacon\C4 inside of it. After their unit producing structures are out, you've practically won. Just destroy the rest of their buildings, but watch out for the minigunners cause they can get pretty darn annoying after a while. Just bring a hummvee and run them over if they give you any trouble.
NOD TACTICS FOR "UNDER"
Since Nod is all about stealth, their tactics work a little more smoothly then GDI's tactics.
TACTIC I
As Nod, the only thing stopping you from decimating GDI's base is the AGT. You must take it out using any means possible. The thing that worked for me was a flame tank. Just drive really close to it and keep shooting. Try to get in back of it after you're next to it because it has a blind spot there. If your vehicle explodes, try to run into the AGT and plant a C4. Just repeat until its taken out. Please note that if the GDI is using engineers you may need more flame tanks to attack in one strike. You'll need to take it out quickly before its repaired.
TACTIC II
Okay, now that the AGT is out, its time to have a little fun. Get enough money for a black hand (the stealth kind), and for maxium results, by a nuke beacon as well. Once this is done, tell everyone to be on base defense, and just run out into the battlefield and enter the GDI base from its main entrance. No one will see you, but don't get too arrogant about it. I know its fun to just sit and watch everyone pass you, but if you stand still for too long they'll see you. Now, run into the barracks with your nuke and wait until everyone is gone (they can see you plant the nuke if they are in the barracks- you're not invisible for a brief moment). Also, try to let no one see you enter, because when doors open mysteriously, they'll know where you are. Plant the nuke beacon on the end game pedestal by holding down the fire button and waiting for it to charge up. IF they're smart and you think they'll find it and dispose of it, plant it somewhere else that's less suspicious. Now, run to another building and put your C4 on a terminal in case the beacon ended up somewhere else then the end game beacon location (it happens all the time and its really annoying). Run out and if you missed the end game beacon location, repeat the tactic again but this time put your C4 on the same building you did last time, and put the nuke beacon in a different building. It takes about three C4 runs to destroy a building, and if you put them all in one spot, it will work very efficiently. After the barracks, you'll want to take out (in this order):
War Factory
Tiberium Refinery
Power Plant
Then you've won without even driving a flame tank inside of the base! A cool thing you can do with the black hand is to stalk people inside of the base after you've unloaded your nuke and C4. Like I remember following an engineer into the freshly destroyed weapons factory. He looked sad and was examining the damage. It seemed he was a little angry, so he took out his pistol and started shooting at the MCT. Then I sneaked in back of him with my laser and shot him! You can guess how suprised he was!
[ February 16, 2002: Message edited by: AngryVortex ]
[ February 16, 2002: Message edited by: AngryVortex ]