4.1 General Strategy
4.1 Unit Specifics
4.2 Build Plan
Zerg are the easiest race to play. They own the early game due to their rapid speed of growth and expansion. They are very strong in the middle game thanks to hydralisks, mutalisks and queens. And they remain strong in the late game thanks to defilers, ultralisks, guardians, etc. The Zerg have so many intrinsic advantages, in fact, that I generally do not find them a challenge to play. For further details, see my notes regarding the Zerg imbalance. With the changes in the Brood War upgrade, the Zerg are no longer the clear favorite, but the jury is still out on whether they still have an unfair edge.
The Zerg's greatest strength lies in their ability to grow quickly. Whereas Terrans and Protoss must march troops across a map to expand, the Zerg can produce troops at any hatchery—the structure required anyway to take advantage of local resources. In the later game, the Zerg's nydus canals can allow troops to be ferried between bases with ease unknown to Terran or Protoss forces. Build as many bases as can be reasonably defended; the resulting mineral and gas flow will allow one to completely overwhelm one's opponents (as if the Zerg needed another advantage). When about to expand, send an attacking force to pen the enemy into his base or just keep him busy. As soon as the new hatchery has finished morphing, start producing drones. Building three at a time will get the expansion up and running far quicker than is possible for Terrans/Protoss. Expand whenever it will at least pay for itself; as long as it will pay for itself, it forces the enemy to further divide his energies thanks to the addition of another target.
Although the Zerg can frequently roll right over their enemies with nothing more than hordes of hydralisks, they are far more effective when their special units are used. Have a defiler or two handy for throwing up dark swarms and plaguing enemies, and bring a six-pack of zerglings to consume—defilers, unlike any other special unit in the game, can recharge near-immediately by snacking on their comrades. Bring a pair of queens along for ensnare, broodling, or infesting a command center. And bring some heavy attack units like guardians in the air and ultralisks on the ground. Plague followed by a hydralisk assault under cover of the dark swarm along with air-to-ground pummeling from guardians and occasional broodling attacks is utterly devastating against any opponent.
Sunken and spore colonies can provide automated defenses for expansions, which allows a Cerebrate to place more troops in the field. They also provide a use for extra drones clogging up the supply limit. They will not protect against heavy assaults, but nydus canals will allow troops to come quickly to the rescue.
I cannot believe how infrequently I see nydus canals used. The Zerg have the ability to effectively move any number of ground units across any distance near instantaneously. A clever cerebrate will leverage this to minimize defensive needs. Against enemy Zerg, it is theoretically possible to leverage nydus canals offensively, but I have yet to see this work in practice.
Although some might claim that zerglings are useless beyond the early game, they may actually play a variety of roles. In the middle and late game stages, zerglings are still useful for attacking albeit usually as fodder. Hydralisks will survive much longer, for example, if their targets are busy killing a bunch of annoying little zerglings. Further, they make the perfect units for reconnaissance. Burying zerglings at strategic points on the map during the early game can provide ongoing reconnaissance far more cheaply than either Terrans or Protoss can obtain it.
Finally, in the late game, zerglings can be used for defiler food. Keeping a six-pack of zerglings handy allows defilers to throw multiple plagues and dark swarms, which are two of the most powerful special abilities in the game. Well-fed defilers are probably the most powerful special unit in the game. The adrenal gland upgrade allows zerglings to remain useful as combatants throughout the entire game. A measly six fully upgraded zerglings can tear down even the toughest structures very quickly.
Hydralisks are the early game workhorse. It is safe to say that the majority of early wins are due to hydralisks. Some people prefer to skip zerglings altogether and go straight for the "hordes of hydralisks" offense. Nevertheless, the value of hydralisks diminishes as the game proceeds. All it takes, for example, is one ensnare, dark swarm or plague to render a squad of hydralisks quite vulnerable. Use them liberally in the early game, but be sure to back them up with special units later on.
Lurkers are a powerful addition to the Zerg arsenal. Prior to Brood War, the Zerg were defensively weak in the early game. But this is no longer the case thanks to the addition of lurkers and the modifications to sunken colonies. A measly four lurkers can tear things apart with shocking speed. And perhaps more frightening is that they are available very early in the game. This is not such a big problem for Terran opponents, but if one can catch the Protoss without photon cannons, then the game is basically over.
Mutalisks, or "muties" as some prefer, are the backbone of the Zerg air force. They are relatively cheap (100/100 each), are fairly powerful (especially when upgraded), and can make short work of most enemy aircraft as well as any air-vulnerable ground unit. Their only serious weakness is an awful vulnerability to stimmed marines or templar psionic storms. Of course, given the stupidity of the computer AI, they have a moth/flame relationship with Terran missile turrets and Protoss photon cannons; one must be extremely careful not to let them wander off! Despite this weakness, however, mutalisks are one of the most flexible units in the game. They are strong on offence and defense, they can attack targets both on the ground and in the air, they are relatively tough, they are relatively inexpensive, and as air units they have no problems with terrain. They can also morph when needed into guardians or devourers, both of which are very useful. A Cerebrate who understands how to use mutalisks well will often be victorious.
Devourers are designed to be the Zerg "capital ships". And they are indeed worthy of the title. A squad of devourers can do enormous damage to targets in the air. And if backed up by hydralisks or mutalisks, their acid spores are utterly devastating. Using them to fire once on each air target seems particularly effective in destroying a group of enemy aircraft—probably because it makes the mutalisk triple-attack ridiculously effective.
Scourge can be either completely useless or utterly devastating depending upon a variety of factors. For example, scourge are the cheapest way to bring down Protoss carriers. Against small numbers (i.e., less than around six) of Terran battle cruisers, they are similarly deadly. They can also impart huge amounts of damage to flying Terran buildings or guardians from an enemy brood.
Queens can be very powerful if used properly. Their ensnare ability slows down both movement and attack rates, which can shift the balance of power in any resource-equivalent confrontation. Their parasite ability is perhaps the best reconnaissance tool in the game. As soon as queens are available, they should be used to infect as many important enemy units with parasites as possible. The ongoing intelligence gathered can be crucial in selecting tactics (see my notes for an example).
Further, the spawn broodlings attack is the single most powerful attack in the game insofar as it is possible. It is the only attack guaranteed to destroy any susceptible enemy unit completely while producing two annoying, albeit extremely weak, broodlings to pester the deceased unit's nearby comrades. A queen with maximum energy can use this attack only once when fully charged, and the attack is valid only against certain units, but it spells certain death for those units against which it may be used. Against Terrans, a squad of queens can completely destroy a force of siege tanks; against Protoss it can destroy those pesky Templar before they can throw a single psionic storm.
Finally, the ability to infest a Terran command center is similarly unique. It allows the Zerg to create some of the most deadly ground units in the game, namely, infested Terrans. When attacking a Terran command center, make it a point to have a queen handy; the resulting infested Terrans can provide one's enemies with serious trouble.
Defilers are probably the most poorly utilized of all the Zerg units, yet they are one of the most powerful if not the most powerful special unit in the entire game. A single plague can give dozens of enemy units a near-death experience, after which even a lowly pack of zerglings can annihilate them. A single dark swarm can provide complete protection from the average ranged assault force, providing time necessary to mass troops or cover for those enemy units stupid enough to stick around. Alternately, it can provide almost complete offensive protection for attacking units—Terran bunkers, for example, are rendered useless except insofar as they contain firebats. Finally, and perhaps most importantly, the defiler is the only special unit in the game that can regain its energy almost instantly. Unlike Terran ghosts, wraiths, battlecruisers or science vessels, or Protoss templar, archons or arbiters, the defiler can immediately regain all of its energy by consuming some cheap zerglings—not a bad trade-off in the thick of combat. Learn to use defilers well, and the Zerg will almost always be victorious.
Ultralisks are another underutilized unit in my experience. They are one of the few units that can weather vulture spider mines, battle cruiser Yamato guns, siege tank fire, reaver scarabs, templar psionic storms, etc. and continue fighting. When facing an otherwise intractable base defense, a squad of ultralisks can often accomplish what other groups of units cannot. Be aware, of course, that as large units ultralisks are particularly vulnerable to the computer AI difficulties (click here for further information). Ultralisks are even more powerful due to their Brood War upgrades. The speed upgrade is essentially mandatory. And the carapace upgrade renders them nigh invulnerable to attacks that do little damage (e.g., marines, zerglings, etc.). If one is going to use ultralisks, one should be sure to upgrade them fully.
Guardians are easily the most devastating of all Zerg units—at least, against ground units. Their range exceeds the range of any ground unit and their attack does a considerable amount of damage. These two factors allow guardians to mow through most enemy defenses with impunity. They are fairly expensive and as such they should be protected against templar psionic storms and Terran wraiths via other support troops. But if a Zerg player is allowed to develop a significant force of guardians, then his opponents have a serious problem. Note well that one does not need a large force of guardians; if one can only afford two or three, they can still be very devastating.
The key to the early game is gaining reconnaissance about the map and the enemy while attempting to build adequate defenses at home. It is also important to harass the enemy; killing his units and damaging his base has psychological as well as strategic value. Pay special attention to destroying his ability to harvest as this is particularly important in the early game. Note well that zerglings and hydralisks alone are sufficient for the early game and, in fact, can bring most games to a successful conclusion in this stage.
At this point, the build plan diverges based upon whether the possibility exists for a quick kill. If one desires the quick kill, then send all available zerglings to kill the enemy harvesters. Otherwise, take the following steps next.
At this point, the Zerg Cerebrate will be in a good position to box in the enemy. Send a sizable group of zerglings and hydralisks to whatever choke points exist to prevent the enemy from discovering the location of Zerg headquarters. If one can box the enemy in at this point (which is quite simple, in fact, for the "Bridge too Far" and similar maps), then one may quickly expand several times with relative safety. By the time the enemy gets sufficient air power to get past the blockade or sufficient ground power to destroy the blockade, the Zerg will have 3 - 5 expansions bringing in minerals and gas. This will allow fast climbing of the tech tree, rapid production of units, and almost guaranteed victory if handled properly.
The dividing line between the early and middle phases of the game is not very clear. Generally, I consider myself into the middle game once I have assembled about half a base; i.e., once I have upgraded my primary hatchery to a lair, have a spawning pool, hydralisk den, and at least one evolution chamber. The middle phase is more difficult than the early phase because more flexibility exists in terms of where to go and what to build. Speaking generally, the most important goal for the Zerg middle game is production of more advanced units. Zerglings and hydralisks will work well by themselves only during the early game; Terran siege tanks or Protoss templar/reavers will make short work of them as matters progress.
The dividing line between the middle and late game is crossed once one has a "complete base"; i.e., once one has the ability to build any Zerg unit capable of being produced. By this time, most (if not all) of the various upgrades will have been researched, and advanced units should already be awaiting orders. If one lives long enough to see the late game as a Zerg Cerebrate, then winning is bound to be painful. Protoss opponents will undoubtedly show up with carriers and archons, and Terran opponents will undoubtedly send battle cruisers and science vessels.