StarCraft: Brood War/Zerg Mission 6: Fury of the Swarm

If you had been enjoying the absolutely abundant resources available to you in the past two missions, then this mission is a bucket of cold water to the face. It is not significantly more difficult than the prior mission (in fact, you might find this one slightly easier), but you start with a strong handicap: you begin with an effectively non-existent tech tree aside from a Spawning Pool, a Spire and a Lair, and you have limited resources on your starting island. This mission will test your resource management skills, particularly since with the inclusion of the Devourer, you will be tempted to spend your cash on costly air units.

Although technically you begin with a main base and four expansions ringing your main island, the comp quickly attacks all of them at once, wiping out the closer two, then the farther two back. They will later claim those resource nodes for themselves. Ignore this for now, and try to get as many of the units present out of the way if possible (particularly the Overlords. Get them to your main quickly, except for maybe those on the VERY top and the VERY bottom. They usually do not get attacked at all, and will greatly serve scouting purposes). At the same time, use the breather afforded by the computer's focus on the expansions to get your economy moving.

Now here's the tricky part. You need to rebuild your tech tree while both maintaining a decent base defense and preparing an attack to reclaim the expansions. Start by building another Hatchery while you are re-assembling your base, bringing the total number of Hatcheries/Lairs/Hives up to three. At the same time, start placing Sunken and Spore Colonies closely around your more important structures, but don't go overboard; 4-5 Sunkens each for both of your starting Hatchery and Lair, along with 4 Spore Colonies each, is about as much as you can spend without severely straining your economy (nor will you need to put all of that in place; you only need about 3 Sunken Colonies on the south end of your island where the majority of ground attacks occur). Start upgrading the Hydralisk upgrades, along with the Lurker Aspect research. The Lurker Upgrade is particularly useful; positioning as few as 3 Lurkers on the south and north ends of the "ridge" that sits in the middle of your island is a major help in dealing with the Computer's drops. You start off with some air units, but several more Mutalisks are highly helpful; generally speaking, the greatest danger you will face from the air to your base is in the form of groups of 5-6 Guardians at most (and usually not that many). At the same time, upgrade the Overlord's Pneumatized Carapace and Ventral Sacs upgrades; your first attack will be a drop. Queens are also highly helpful in this mission, with their inbred Parasite ability.

Once you have at least 24 Hydralisks and 6-8 Lurkers, pick either the top peninsula or the bottom peninsula to reclaim from the enemy Zerg. They established bases there, so prepare for some resistance in the form of Zerglings, Hydralisks, Lurkers, and even some Ultralisks at worst. Just make sure to take full advantage of your Lurkers; since they won't harm your own units, use them to cover a retreat of your Hydralisks if necessary, and to wipe out waves of weaker Zerg ground units. Start with clearing the back base of whichever peninsula you choose, and sweep westward to destroy the second base. While you are sweeping forward, re-inforce your attack force with new Hydralisks and IMMEDIATELY start building a Hatchery at the newly cleared back base - by now, you are probably both nearly dry on minerals and sucking fumes from your starting geyser, so get the Hatchery up and running, and build a Nydus Canal to your main base. Re-inforce it with a few Sunken and Spore Colonies back up by some burrowed Hydralisks to help kill any pesky Guardians. After wiping out the westmost base on either peninsula, you'll come to a chokepoint leading to said peninsula, whether a ramp or pathway. Burrow at least five Lurkers on the pathway - the comp is not quite sophisticated enough to stop this tactic unless they happen to bring an Overlord by chance, so it will help slow down attacks by ground from either of the two big Zerg enemy bases.

If you want the minerals and/or to be thorough, you can take both peninsulas (reclaiming your entire original area), although it's not necessary and will be more difficult to defend. The resources from one peninsula, as long as you don't put the attack off for too long, should be enough to last you the rest of the game.

Once you've set up the Nydus Canals and defenses for both of your two brand new expansions, and are harvesting a steady set of resources, start preparing for your attack on either the north-western Zerg Base or the South-western Zerg base - whichever base is directly in the pathway to the Terran base by ground from the peninsula you just expanded to. You should have at least five Hatcheries/Lairs/Hives at this point (the two originals at your island, the additional Hatchery on your island plus the two expansion Hatcheries), and considering building 2 or more additional Hatcheries for production purposes. Use the Nydus Canals to concentrate the force near the choke point leading into your westmost expansion. At the same time, get an Ultralisk Den, and get the upgrades rolling for them if you haven't done so already. Queens at this point are strongly recommended; while making the preparations for your major assault, have your Queens go out and lay as many parasites as possible on the Zerg Base you will be attacking.

Your weapon of choice is a Hydralisk Hammer: 5-6 forces of 12 Hydralisks each, led into battle by 10-12 Ultralisks. The Ultralisks go in first mainly in order to draw the enemy fire so that your Hydralisks can all make it into the enemy base to cause the real damage. Move them as close as possible to the Zerg Base you are assaulting without drawing enemy fire, then launch the attack all at once, using the Attack command to send it the Ultralisks first, followed by your Hydralisk forces (micro the Hydras if necessary in order to kill dangerous units like Lurkers). Bring along at least 1-2 Overlords to spot Lurkers and other burrowed units.

Once you've annihilated the Zerg Base of your choice, this mission becomes considerably easier, since once you assault the Terran base across the bridge, the other Zerg base generally won't intervene in any real numbers as long as your units don't try to cross the bridge into their territory. At the same time, the Terran base doesn't have anything defending it beyond a number of Marines and Firebats with Medics (who have been assigned special names in this mission, but remain unchanged otherwise), so once you get past the Bunkers on the other side of the ramp into the base, victory is a breeze.

Re-build a group of Ultralisks - the bigger, the better. If your Hydralisk forces have taken losses reducing them to below 36 in number, rebuild to at least that amount. Once the force is ready, run your Ultralisks across the bridge to the other side, and then have then start attacking everything nearby. DO NOT use the Attack command to send them across; they will clog the bridge only allowing one or two to attack period, which allows the Terrans to pick them off. Once the Bunkers are gone, feel free to use the attack command with your ultralisks as long as they don't go near the bridge leading to the other Zerg base. Bring your Hydralisks over to help with the assault, and to begin the search for the Scientists. The mission is essentially over once you have your large force in the Terran base; with their weak defense consisting mainly of infantry, you can move your Hydralisks around with impunity to target and kill the Scientists. When all 30 are dead, you've won.

An alternate method to get across the bridge is to use the five or six lurkers burrowed at the junction to burrow at this bunker-defended ramp. Leapfrog your lurkers closer and closer to the bunkers, but be careful of the Missile Turret to the south of the ramp. You may only be able to get one lurker in range to attack the bunkers, but one is enough to eventually clear them. Then just walk your Ultralisks in with your Hydralisks.
 * Using lurkers to advance