Starcraft – How to select a mixed group of troops with the Stimpack option showing

For protoss you have to make excellent use of Sentries to delay your enemy. If possible, try to split his army in two with Force Field(s) and take on that half by itself with your zealots, sentries, and stalkers. You won't be able to take him in a head-on fight as Marines/Marauders dominate your T1 units.

Use this delaying tactic to get a few Immortals as soon as possible and transition into Colossus with the range upgrade. The splash damage is very effective against the tightly clumped Bio Ball, while Immortals can take many hits from Siege Tanks. Use Blink Stalkers to get close to the tanks and focus them down. Note that once you have a few Colossi, your opponent will usually get a few vikings to counter them, but focus them down quickly with your stalkers.

Honestly, it is a very difficult thing to beat as Protoss if your opponent is of better or equal skill, especially since you have to tech to very expensive units just to counter his (mostly) T1 army. You'll just have to delay and outplay them and not make any mistakes, and make sure you are very proficient with your Force Field and Guardian Shield usage.

Another option is to go High Templars with Psionic Storm and Feedback on the Medivacs, but I rarely go this route as it is too gas-intensive and higher level Terran players will just use Ghosts which nullify High Templars with their EMP ability (Removes all energy and 100 shield points). Not to mention if your clump of High Templars goes within range of a Siege Tank you're dead meat.

So the first problem you have is that these are the units you've listed:

• Marine
• Marauder
• Medivac
• Siege Tank

If I were to present a different list of units you might say Zerg is unbeatable:

• Ultralisk
• Corruptor
• Crackling
• Broodlord

So instead of trying to deal with everything a Terran player might do, let's break BioMech down into stages and look at what you can do at each stage.

3 Rax

BioMech usually starts as a 3 Rax opening (though it can starts a 5 Rax Reapers, or Early Hellion Harassment). So your early game should largely be based around dealing with Marine/Marauder forces. There are a number of good strategies to dealing with MM, but the most effective is usually Banelings.

Banelings do a very heavy amount of splash damage and since MM tend to ball to form the best fighting force, Banelings are very effective against them. I've discussed Baneling use at length, but even with them you'll need something to back up your Banelings. Usually this means Roaches or Speedlings. As Banelings will destroy most of his force you're using these troops to mop up and possibly go on the offensive.

Alternately, if you want to skip Banelings and go for early Lair, a Hydra/Speedling force can be every effective if you can flank. This usually involved engaging at a choke (where your Hydra have better surface area) and running Speedlings around the back of his troops to prevent escape. Good Terran players have a "feel" for the timing on a Marauder reload and can usually micro Marauders without any damage loss. This is why its so important to get the Speedlings behind the MM Ball.

MMM

The natural progression of 3 Rax is into MMM. The reason for this is that Stim is a very dangerous tool and if your opponent forces you to Stim at the wrong time, that's a good chunk of HP missing (especially from the high dps Marines). Medivac's largely deal with this problem and increase the effectiveness of Stim. Since Stim is so powerful you'll almost immediately feel when this is happening.

You deal with an MMM much the way you deal with an MM force, there is little difference here. It does become worth starting to get Roaches as a meat shield, and I cannot overstate how effective Infestors can be at this stage. Infestors not only do heavy damage to bunched units, but will also prevent his Stimmed army from getting away from your slower Roach/Hydra. The other thing to watch for is try to engage on creep. Since he'll be using Stim more liberally, you don't want your units getting kited.

Early Tank

If your opponent sees a lot of Banelings he may instead go early Siege Tanks instead of Medivacs. If you force your opponent to do this, there is a good chance you can pull out a win. Since this is the time he's largely switching from 1 base to 2 base his production won't be in place to support a MMTank build. As a result he's going to cut production on something, usually Marauders. Depending on what this something is, you can exploit this for a much easier win. If he cuts production on Marauders, then you can flood him with Roaches. If he cuts Marines, Speedlings or Doom Drops will spell the end for him (as his army will be tiny).

Early Tanks are usually a knee jerk reaction to damage by Banelings. As a result, about 75% of the time you should be able to roll him as his strategy will be in disarray. The remaining 25%, stay calm, scout him, and look for what you can exploit.

BioMech

Eventually he'll transition from Early Tank or MMM into BioMech. By now you're getting into late game and will have Tier 3 units at your disposal. If you're playing well you should be sitting on 4 Bases to his 2, and this will be a piece of cake. Since you asked this question I'm guessing you're not playing well at this point, which usually means 3 bases to his 2. If you find yourself in a situation of 2 of your bases to 2/3 of his, you need to seriously reconsider when to expand.

At this point you want to start transitioning into your end game strategy. Usually this means: Ultralisk/Crackling, or Corruptor/Broodlord/Roach, or some combination of end game units. The end game part is key. If you find yourself against a large MMM ball supported by Tanks and you're still running around with Baneling/Roach, you've essentially forgotten to tech while your opponent hasn't. To this end: Siege Tanks die quickly to Ultras, BioMech has a lot of trouble with Broodlords, etc.

Now if he rushes BioMech and cuts production of his army, there is a chance you could see 1-2 Tanks/1-2 Medivac/A handful of Marines. This means he's overspent on Tech and you can exploit this for victory. In a situation like this, I can not over state the effectiveness of Speedling/Baneling. If you get those Banelings in there it'll clean his Marines, and your Speedlings will mop up. Since his teching means he doesn't have a ton of Infantry building structures (and other units take much longer to build), you should be able to get your Speedlings from the battle, into his mineral line VERY quickly. A 1:1:1 opening can be effective against Zerg, but if he's using it to go BioMech he's throwing that effectiveness away (as opposed to going Viking/Hellion harass).

Remember, No man can do all things so don't worry so much about how to counter A,B,C,D and worry more about, how do I use what I have to deal with what he has.