Mech (vs. Terran)
Focuses on mass production of units from Factories, with some support units from the Starport. Mechanical units have higher health and raw damage output but suffer from immobility and slow rates of fire, making them weak to the melee units commonly found in Zerg and Protoss unit mixes; thus normally needing Biological units for the high rate of fire. Terran vs. Terran however is more of a positional game, focused on Siege Tank production and carefully placing units to slowly leapfrog towards the opponent's main base while distracting and harassing with Hellions.
- Siege Tank: Build in highest count possible to cripple the opponent's army through direct combat and maintain position on the map. The damage output in Siege Mode or in normal tank mode makes this unit devastating to attack head on.
- Hellion: Used as a mineral sink for harassment and as a meat-shield before Thors are plentiful. Throughout the entire game Hellions will also be expendable as the unit serves no other purpose than harassing the opponent's mineral lines and countering high Light attributed unit counts.
- Thor: The health of the unit and damage output makes it a strong unit for standing at the front of the battle and taking the firepower head on. By the time a Thor has been taken down the damage dealt to the opponent's army will be much greater as long as Siege Tanks or additional Thors are also firing. Thors are generally most effective in mech-versus-mech battles, as its large size will negate a lot of the Siege Tank splash damage. Anti-air splash damage also makes the Thor effective against every air unit except the Battlecruiser.
- Viking: Firstly produced to prevent the opponent from abusing the Mechanical units weakness to Starport units and Medivac-based drop tactics; as well as the sight range advantage over the opponent. Producing these units is not optional as the opponent can abuse the poor mobility of Mechanical units with Banshees or Medivac drops and later on in the game with Battlecruisers. Simply having more Vikings is of utmost importance in any Terran Vs. Terran match-up.
- Planetary Fortress and Missile Turret: Used for Zoning off different attack paths the opponent's more mobile bio and air units can take, going overboard on these structures is not a disadvantage either as the bulk of the cost is in minerals. You will often see a large amount of turrets surrounding a meching player's base to defend against drops and even near the Siege Tanks, especially if the player does not have air superiority.
Supplementary Unit Roles
- Medivac: Only for dropship-based Hellion harassment. Using Medivacs to bypass the opponent's army and attack workers directly after Hellions can no longer simply out maneuver the opponent or should the opponent wall-in. Players generally don't make more than one Medivac as it doesn't have the dual-functionality it does with an infantry-based army, which Medivacs can heal.
- Banshee: If you have the superior Viking count, a few Banshees can be used to push your opponent's Siege Tank lines back unless he has a Thor or Missile Turrets defending them.
- Battlecruiser: Generally the unit that you get in the late-game if neither player can gain a sufficient advantage with the mid-game mech battles. Battlecruisers can kill or at the very least push back Siege Tank lines just like Banshees can, but are much less vulnerable to Thors and Missile Turrets. The only real response to Battlecruisers are Vikings as Thors do too little damage while Missile Turrets and Marines can be dealt with, especially with Siege Tank support.
- Raven: Getting a Raven early on can be extremely useful as it will allow you to detect any cloaked Banshees and harass with Auto-Turrets, but most importantly, Point Defense Drone can help you in Viking-versus-Viking battles, and will help a lot if your opponent is going for a Marauder-heavy unit composition. Later in the game, Seeker Missile is good in air battles as it can do a lot of damage or force your opponent's Vikings to run away from the battle.
Positioning and micro
Siege Tank positioning is the most important part of mech play. If your opponent is going bio or biomech you always run the risk of getting caught off guard by a quick stim while you're unsieged, and if both players are going mech, whoever can siege in range of the other player first often has the advantage. Using Hellions and Scanner Sweep to find out where your opponent's army is positioned is key, as it will allow you to know when you need to engage Siege Mode.
Choosing where to siege is a somewhat easier, but much more important part of mech positioning - especially early in the game when your tank count is not very high. The general rules of arcs/concaves and chokes apply doubly when you're going for a tank-heavy style. Try to siege up just in range of any chokes available to you, and when moving out into open terrain you either need to know that your opponent's army count has been decimated or you need to be extra careful, leapfrogging slowly and spending extra scans/forward Hellions to reveal the enemy army's location.
Hellion positioning is also important. You want to keep at least some of them active on the map to harass and forcing your opponent into a defensive position, but you also want to keep the bulk of them near your Siege Tanks to soak up damage if a confrontation should occur.
When advancing with Siege Tanks, Hellions and Thors should be spread out and sent in the front to soak up damage while your Siege Tanks are advancing and going into Siege Mode. You want to send them in as late as possible - if you send them in too early, they take unnecessary damage because your Siege Tanks aren't in range yet, but if you send them in too late you may lose Siege Tanks. Ideally you want to move your Siege Tanks forward first, then time it so your Hellions and Thors get in range of your opponent's Siege Tank line just before your Siege Tanks do.
Air positioning can also be important - if your opponent has Marines, you don't want to send your air too far forward, you want them defended by your Siege Tanks. Against Thors (and Seeker Missile) it's very important not to stack your air units as that will allow the Thors to do maximum splash damage. It's also very easy for your air units to get drawn in by your opponent's forces, and if you don't pay attention some of them may get isolated and killed.
Before reaching three bases, there's generally not that many upgrades involved in mech play - Infernal Pre-Igniter is the only required one. Attack upgrades for mech are not very useful against a Marine/Marauder-heavy opponent as it takes a lot of upgrades before they actually make a difference in how many tank shots it takes to kill them. Armor upgrades may let your mech army survive longer, but against a bio-heavy style your goal should be to avoid taking those shots in the first place.
If both players are going mech, upgrades are a bit more favourable. A big reason for this is that an Armory is required for Thors which soak up a lot of tank damage. Some important Armory upgrades are:
- If your opponent has no mech armor upgrades, +1 attack on your Siege Tanks will allow them to kill your opponent's Siege Tanks in 3 shots instead of 4 (while sieged)
- No matter the armor upgrades, +1 attack on your Siege Tanks will allow them to kill your opponent's Thors in 7 shots instead of 8 (while sieged)
- Until your opponent gets +2 armor, +2 attack on your Siege Tanks will allow them to kill your opponent's Thors in 6 shots
- +1 air armor on your Vikings will allow them to survive one extra volley from other Vikings until your opponent gets +1 air attack
Later in the game, if you transition into mass air, air armor upgrades get very important, especially if you have the superior Viking count. The only ground-to-air capabilities Terran has (Marines, Thors and Missile Turrets) don't do a lot of damage but do it very quickly, which means that armor upgrades are very effective.