Mech (vs. Zerg)
Infantry formations and micro suffer greatly versus Zergling/Baneling armies (Zerglings require the infantry to ball up, whereas versus Banelings it's good spread them out) while additionally Concussive Shells is not overly effective versus the greater Zerg numbers.
Terran Mech suffers far less from these disadvantages and especially the splash damage that Hellions, Tanks and Thors deal are particularly effective versus the clumped Zerglings, Banelings and Mutalisks (and, to a lesser degree, Hydralisks and Roaches) that Zerg has.
An important feature to note is the level of threat that Siege Tank or Thor attack timing cause and will take the opponent's entire army to fight head on, if early enough, Hellions however have limited use in direct battles but attacking where the opponent's army is not is Hellions specialty.
Mech "packs a punch". You can do a lot of damage with a good mech army so usually the Terran builds up to a single big push. With an early game push you need to do significant damage and late-game you pretty much need to all-out kill your opponent. If not, Zerg can out-expand you and macro back up much faster, as Mech macro is among the slowest in the game.
Factories and their units are costly, especially on the Gas side of things. Consequently, either an early expansion or dealing damage with your first push or rush is pivotal. Timely expanding is also important as any reserves will last only so long when building expensive Tanks and Thors.
Mech's great weakness is mobility. Early midgame, this can be helped by using Medivacs for drop-harass, but generally you will not be able to move to-and-from with large portions of your army. Therefore take note of two things:
- Upon moving out it is important to gain a significant position, preferably in range of his natural or at some other critical sweet spot on the map. You will not be able to retreat quickly in case of a counter, so make your push worth it.
- As a precaution to not being able to run back and defend you need to be wary of the Zerg's mobility. Counters exist in Mutalisk backstabs and Nydus worm attacks. Prepare for these possibilities: Make sure Turrets are in place (or even a Thor) and leave some units behind if you suspect a Nydus Worm attack.
Because Mech units take a long time to produce out of expensive structures, it is difficult to reproduce mech units after a battle has been lost.
The Hellions are a way of harassing the Zerg's outer expansions. Send them out to scout his expos and kill your opponent's drones. Be wary of an attack on your army while your Hellions are absent. Never overcommit. Used in the same fashion as Zerglings for back-stabbing the opponent's poorly defended expansions.
Hellions are there to deal great damage to Zerglings, Banelings and Hydralisks. Under the cover of Tank shelling engage these units with the Hellions. They are less effective versus Roaches, but you need to use them to keep Roaches away from your Tanks. Kite with the Hellions to take minimal damage while the Tanks deal with the Roaches.
- Terrible, Terrible Damage
Tanks are there to deal damage. Remember that Tank dps is greater unsieged than in siege mode. However, as the Zerg is usually in greater numbers, the splash damage of a sieged Tank really pays off. Your Tanks are the backbone of your army and should be protected (by your Hellions/Thors) at all times.
- Anti Air
Although slow, Thors deal massive damage to Mutalisks. They act as part of your base's anti-air defenses before moving out and initially your main anti-air upon moving out.
- NOTE: Although effective versus early Mutalisks raids, a Zerg can, by splitting his Mutalisks, drastically diminish your Thor's effectiveness. If your opponent heavily relies on Mutalisks, make sure to repair, get upgrades, support your push with Turrets and push earlier rather than later. The Zerg player may also utilize the 'magic box' to potentially eliminate all splash damage done by your Thors.
Keep your Thors in front of your Tanks in ground-to-ground combat. They do significant (albeit not critical) damage versus Hydras and Roaches and can soak up a good amount of damage while your Tanks fire away.
SCV Use them to repair and build Turrets with your push. You can even push up small walls to soak damage while your units fire at his.
Turret Essential versus any Zerg that heavily relies on Mutas or burrowed Roaches. Use them for detection to save valuable scans.
Viking Great scout and punishes stray Overlords. If he allows you to get more you can keep building them to completely negate any Spire units later on. Taking air dominance like this allows you to expand to islands. Mind that you do not need as many Thors now and should focus Factory production on Tanks and Hellions. Furthermore, Vikings are essential when you have to deal with Brood Lords.
Raven You can get one or two for mobile detection, keeping them with your army to deny surprise burrowed Roach attacks and pick off Creep Tumors. The Point Defense Drone is good versus Hydras, but the Seeker Missile upgrade generally does not pay off.
When pushing anywhere (be it to get in his face, be it to secure a third) place your Tanks spaced out to avoid friendly splash. Also build Turrets to assist your army. Slow pushing is good for gaining some ground (for example to an expansion) but will often be open to letting the Zerg build up to an effective counter - be it by expanding more or backstabbing while you're half-way away from everything.
A well fit out Mech army does not have any unit>unit hard counters, however Brood Lords are a soft counter to an army composed of pure Tank/Thor/Hellion. Until you add Vikings, you can effectively stall his push, however the main concepts are still out-expanding (and out-macroing) and abusing mobility (backstabbing T's macro facilities).
As far as units go, Roaches are the sturdy option. If you can burrow-move them and get the close to a Thor, they can try to take it down, freeing the way for Mutalisks. Infestors with Neural Parasite on Thors or Fungal Growth on the Hellions can also prove effective. As Zerg, players need to be mainly on the watch for a single big push the need to use their time to spread creep and set up flanks for when it comes.
Zerg can also use their better mobility to flank and backstab with Mutas or Zergling run-bys. Creeping up the map greatly enhances this maneuverability and Terran players should keep an eye out to kill off Creep Tumors. Other options are the Nydus Worm and the Overlord Drop. These are both effective ways of punishing a Terran whose army is out of place.
In return Terrans need to scout ahead (with Scans/Hellions/Vikings) for the army when pushing up to the Zerg's base.
The Infernal Pre-igniter and Siege Mode should be a no-brainer, but also Armory upgrades are critical to get. Tank damage upgrades will also affect splash, making them much more effective. 250mm Strike Cannons for Thors used to be very effective against Ultralisks, but as of Beta Patch 16, Ultralisks are immune to stuns and snares. Thors can also 2-shot Mutalisks once Vehicle Weapons Level 2 is finished and Zerg's Flyer Carapace Level 2 hasn't been finished, which makes Thors more powerful against Mutalisks in the late game.
- qxc vs Strifecoe on Metalopolis - qxc using all-out Mech with Viking/Raven support versus Strifecoe.
- GoOdy vs Col.Catz on Bel'shir Beach - Force Commentary
GoOdy opens with Reaper, Hellion and Banshee harass before starting Double Armory and going up to 3 Factories, but the diverse unit mix seems to throw the opponent off for most of the game leaving GoOdy with all the initiative until losing the first major battle. But the Hellion backstab was quite funny.