StarCraft: Brood War/Terran Mission 5A: Emperor's Fall (Ground Zero)

Getting Started
You start with only two SCVs and one Marine. You also have what appears to be all the supply depots you will need. This turns out to be incorrect; enemy nukes will blow up every last supply depot you have, and leave you with only your Command Center. However, you can save some of your buildings if you lift them off. Your first move (after you get your SCVs to mine minerals and your starting Marine in your bunker) should be to liftoff your Barracks and Factory and bring them past your Mineral Fields, if not at your mineral fields in order to save those buildings. Although it's not the end of the world if you don't save them, you will waste extra time and money rebuilding them.

When the enemy starts nuking in your main base, you will get many dropships with units in them, as well as two Battlecruisers. You cannot save these, however; they will be destroyed in the nuke whether you like it or not. Fortunately, you will get 2 more dropships later, one with eight SCVs and the other with eight Marines. This is after your nukes blow up. Just remember though, you should have built as many SCVs as possible before your reinforcements have arrived, so that you can mine minerals faster (remember that you have only 10 supply count!) Don't even think about building extra buildings before the nukes land in your base for obvious reasons, and there are also burrowed and invincible Zerglings in your base to stop you from building until the nukes are gone.

Your immediate task now is to have at least two SCVs building Supply Depots continuously, and have at least one SCV repairing your severely damaged Command Center. If your Barracks and Factory have been destroyed in the nuke as well, you have to get working on them fast. Reattach a Machine Shop to your Factory and build a Starport. Since you have many resources in your main base, start with 400 vespene gas, and have two separate resource nodes up north (one in the middle west and the other in the northwest corner), the initial setup won't be difficult.

Setting Up Your Defenses
Got enough supplies to feed your troops? Good, because now is the time you pay extra careful attention to what happens in your base. You will have vicious attacks to your base, and you have to be careful about how your units and buildings were placed. Below are a few examples of attacks you will get early in the game. In every case, a Science Vessel in front of your defense lines prove useful.
 * Large Infantry/Mechanical Waves: You will definitely face this in every scenario involving a large enemy Terran base. The Dominion, especially Red, will bring a mixed combination of Marines/Firebats/Goliaths with one or two Siege Tanks, sometimes with Vultures also. You should have a Bunker with Siege Tanks surrounding it in a semi-circle; the uncovered part would be where the enemy would attack you from. The Marines in your bunkers can handle units that get close (such as Firebats), while your Siege Tanks will splash units that are still coming. The Siege Tanks you may get in this wave will have a little trouble coming in because of other units, but make sure your Tanks are the first to hit them.
 * Tank-Only Waves: This is more common with Blue. Occasionally, you will find 3-5 Siege Tanks coming to wreak havoc on your defense. You need to outnumber their Siege Tanks to stop this attack. Use defensive matrix on any of your Siege Tanks being attacked, and have the Science Vessel provide sight constantly. Any Wraiths or Battlecruisers can also help you deal with this.
 * Groups of Wraiths: The Dominion loves to mix things up for the UED, and its most favorite unit for attack is probably the Wraith. If you don't have enough Missile Turrets on their path, expect them to attack your Siege Tanks/Bunkers or your mineral/gas area. This is why you want Missile Turrets accompanying each one of your defense areas.
 * Ghost Waves: This is arguably the worst and the most frightening attack, especially in this scenario. The enemy has four Nuclear Silos, and they will certainly use more nukes on your buildings and forces. Only Red will nuke you, but both Dominion forces will cloak their Ghosts and lockdown your mechanical units.

There are, of course, priorities to where the enemy will nuke. It goes as follows;
 * Permanent Detectors: If they nuke your base, it's almost always on a Missile Turret. If they go for your defenses, it is often an area accompanied by a Science Vessel. Keep at least one Tank near each turret, and scan areas where you have turrets. They are actually more likely to strike your attack force, so patrol your Science Vessels near every one of your attacking groups.
 * High-Calibre Defense: If they don't find detectors, they will most certainly nuke at wherever many of your units were gathered; this would mean areas with clusters of Tanks/Goliaths/Bunkers. Patrolling Science Vessels can usually solve this problem.
 * Resource Nodes: They will find and strike buildings such as Refinery or Command Center, hoping to destroy as many SCVs as possible. Don't worry about this nearly as much as where you have gathered your offensive and defensive units, along with detectors.

Remember the final level of the Terran campaign in the Original Starcraft (The Hammer Falls)? You may have had to deal with Ghosts using lockdown on your Siege Tanks, Goliaths and Battlecurisers, and then maybe face the enemy Siege Tanks that take down your locked units. You might face a similar threat here, but this time, there is something you can do to counter this. Have at least two Medics near any large group of your mechanical units, and use Restoration on them if they become targets of lockdown. Have a Science Vessel find the Ghosts, and viciously attack them back. If an enemy Science Vessel uses Irradiate on one of your Medics, the other can restore that Medic and heal her.

The Attack
The enemy here is notorious for their number of Goliaths, Turrets and Ghosts. Especially with the way the enemy defenses were set up, it would be very difficult to attack from the air. Instead, just take about 18 Siege Tanks, 12 Goliaths, 2-6 SCVs, a Science Vessel and at least two Medics. Fortunately, the Dominion never uses Medics (no blinding your Science Vessel) and do not lockdown your Science Vessel until they get all the other stuff. As long as you don't lose the Science Vessel, one would do. Siege your tanks very often, and eliminate any targets you find. Your Medics should restore any units under lockdown or irradiate. Your SCVs should either repair units or build Factories (Yes, you may want to build factories in the middle of their base to replace your lost units, considering the enemy is far away from your base). If you come across many enemy Siege Tanks, don't try to fight them off. Instead, shoot at other targets that they use their Siege Tanks to respond to your attack. When they come at you, start firing at them. Whenever you advance, make sure your Science Vessel is taking the lead and shows you what's ahead; you will come across many Ghosts, Wraiths and Spider Mines, and you want to make sure you can see them first. Once you have cleared Red's main base, you will be able to take down Mengsk's Command Center with ease.

Defending Your Base Against the Early Nukes
Although difficult, it is possible to have most of your buildings and reinforcements survive the nukes near the beginning of the game. To follow this strategy, you need to build three Vultures and research Spider Mines. On all entrances, put down three mines each, a considerable distance away from each other. If you are careful enough, you might stop all the ghosts before the nukes fall.