StarCraft II - Terran Infantry In-Depth Stats and Strategy
The only thing better than one grizzled Marine, is a hundred of them firing at the same target. Stimpacked, of course.
Cost - 50 minerals, 1 supply
Build Time - 25 seconds
Combat Stats - 45 (55 upgraded) HP, 6 damage with +1 per attack upgrade, 5 range, 0 armor. Light, Biological armor types.
Can shoot land or air units.
Early Game - Unless going against an opponent massing purely armored units (Stalkers, Marauders, or Roaches), you'll want to have a good chunk of Marines with your force at any given time. After your first 2 mules or so, you should have an abundance of minerals to spend, and this is generally where they go. Your first Barracks should have a Tech Lab add-on so you can adapt early to your opponent, but your second should be dedicated to pumping out the trusty Marines. Since they have a fairly high build time for being such a frail unit, you can be vulnerable early if your defenses are only Marines. Use a bunker or two at your expansion/ramp in order to secure your expansion from early aggression.
Mid Game - Middle game for Marines is about when your first +1 attack finishes and Stimpacks are done. Your Marines are killing machines at this point, but if you're going heavy on the Marines, the opponent's counter is either ready or in progress. Send out SCVs to figure out what your opponent's answer is, and prepare supporting units to fight it so your Marines can keep being the strong arm of your force.
Marine Counters and Your Answers
Banelings - Hellions, run away while stimpacked until they are picked off.
Infestors - Ghost EMP, Siege Tanks
Colossi - Vikings, Siege Tanks
High Templar - Ghost EMP, Hellions
Ravens - Ghost EMP, Vikings, even a Thor
Hellions - Siege Tanks, Marauders with Slow
Sentries - Ghost EMP, cry softly as there's nothing you can do about forcefield.
Late Game - Once Medivacs and your opponent's counter units come into play, you have to be a lot more careful with your Marines. You cannot just stand still and fire when all of the area of effect weapons are on the battlefield. Micromanagement comes into play more than ever once the Colossi storm the battlefield, or the High Templar storm it quite literally. Marines are quite nimble when under the effects of Stimpack, and need to be moved away from these chaotic abilities before they are charred to a crisp. Keep upgrading your attack, as Marines are one of the most effective units in the game to be upgraded for what they do.
You might be tempted to use Medievac drop tactics in the Mid and Late game, but be careful and drop only to harass, not to destroy. An intercepted drop with half of your army involved usually spells instant defeat. Stimpack and take out what you can--key tech structures or workers are your highest priorities. If you can get away with it, take out your opponent's Nexus/Command Center/Hatchery to really punish them. Be careful when moving Medievacs with your army though--issuing attack move commands or move commands across long distance will have the Medievac far ahead of your army. This can either mean the Medievac is picked off immediately, or your army is picked off with no healing available. Either one is trouble, so move your forces slowly if you're controlling them all in one attack group.
The Marauder is here to stay.
Cost - 100 Minerals, 25 Gas, 2 Supply
Build Time - 30 Seconds
Combat Stats - 125 HP , 1 armor, 10 damage and +10 bonus damage vs. armored (Each +1 per weapon upgrade), 6 range. Armored and Biological armor types. Can be upgraded to slow the units they attack briefly.
Only attacks ground units and structures.
Early Game - A quick pack of Marauders can force your opponent to tech switch in a hurry. Marauders demolish the units they counter, with good range, outstanding damage, and the slow effect ensuring no one can escape once focused. Common rush tactics in multiplayer almost always involve a pack of Marauders simply because they're so good against their counters, and when the counters are dead, they demolish structures as well. Defenses go down in only a few volleys from Marauders. The only thing you have to fear with these is fear itself--no unit aside from the Marauder has a big bonus vs. Armored units early on. Maybe you should fear air units, or mass Zerglings... but once your Concussive Shells upgrade is finished, micro your units carefully and keep Zealots slowed and chasing you around endlessly. Each one that dies is another Marauder's worth of minerals advantage to you.
If you are going for these early and not focusing on Marines, go for at least 2 Barracks with tech labs and get both gas geysers up ASAP. You need the extra gas to get your critical upgrades for these out--+1 attack and armor, Stimpack, and Concussive shells. This is 400 gas, and unless you don't plan on teching at all beyond these, you'll need the 2nd geyser quickly to afford any of those while producing Marauders full time. Strike early and strike hard. You should try to hide your Marauder pack to the best of your ability or you'll see Air or anti-armored out in a hurry.
Mid Game - Now that the counters to Armored are in the field, you need to be a little more careful with these. Immortals love Marauders. Their shields prevent the bonus damage from being applied, and they kill a Marauder in 3 hits regardless of attack or armor upgrades. Mutalisks can have their way with you, and Hydralisks out-damage you since they don't receive the bonus damage, being light units. Siege Tanks can take advantage of your clustering fire line and demolish you with splash damage while you work on the forces up front. Micromanagement again becomes the name of the game, and you need to focus fire the targets these are effective against, and let the rest of your army handle the remaining units. You don't have to worry about the main counters to Marines for the most part due to how tough the Marauder is, and how quickly it can demolish a few of the counters--Infestors and Colossi namely go down in short order to Stimpacked Marauders. If you want to keep giving these a whole lotta love, make sure you go for Medievacs. They may have a ton of HP for infantry, but it wears down over time with each Stimpack.
Marauder drop tactics are a little more effective than Marine drops, but the main problem is having zero answer to air units. Your Medievac can simply be assassinated and then your Marauder force is stranded, without healing. The good news is that Stimpacked Marauders can demolish whatever you dropped them off to kill in short order, and hopefully you can manage to make a somewhat fair exchange out of the deal, be it a Nexus or several tech structures demolished.
Late Game - Marauders are extremely effective against Ultralisks, Thors, and Colossi. If your opponent brings any of these onto the field, a pack of Marauders can bring it down with lightning speed. These fare poorly against heavy air, but no worse than any other unit that can't attack back. For their cost, they're still quite tough and since most mid and late game units are Armored, should remain a staple unit in your force. Marines and Marauders comprise the bulk of almost every Terran player's force, and usually in a 2 or 3 Marines to 1 Marauder ratio. When using these, make sure they are leading the pack. They have enough durability and range to engage any force, and since they engage first, if your opponent decides to immediately retreat you'll score some free kills.
A rejected costume design for
The Dark Knight, used as concept art for the Reaper.
Cost - 50 minerals, 50 gas, 1 supply
Build Time - 40 seconds
Combat Stats - 50 HP, 0 armor, 4 damage per shot, +5 vs. Light (Each +1 per weapon upgrade), fires twice per attack. Hurls demolition charges at buildings, dealing 30 damage each. 5 range, moderately fast. Can be upgraded to very fast.
Only attacks ground units and structures
Early Game - The only time to effectively use Reapers is right from the start. If you're going to get Reapers, build directly to them. This means an early Barracks around your 10th SCV, before your supply depot, and an early Refinery while this is building. Start a supply depot once those two are started, get two more SCVs in the Refinery when it finishes and then immediately drop the Tech Lab when the Barracks is complete. Scout with either the Barracks, or the Supply Depot SCV and check your opponent's location and see just how vulnerable they will be to the rush. If it's a Zerg, watch for a fast expansion. If it's a Protoss, if they do more than one Gateway before their Cybernetics Core, Reapers will do great damage. Typically you won't run into Wall-ins in Terran vs. Terran, but if you do, see if their Barracks' Tech Lab is already complete like yours. If it is, you might expect the same rush coming to you, or an early Marauder, both of which should make you reconsider this attack.
Once you have two Reapers, move out. If you are training a third, set the rally point to right outside your opponent's base or right up their cliffside. Skirt around the outside and make your way straight for the mineral line. Unleash hell--it only takes 3 double-shots of the Reaper to take out a worker. Do as much damage as possible, and if the response is Zerglings or Zealots, just run away from them and take them out slowly. So long as you're not on the creep, you can do this to Zerglings. The moment a Queen or Roach comes out, your attack is going to fall apart quickly and you should retreat with your Reapers intact.
At this point you can switch to an offensive contain. The Zerg probably is thinking about, or already has put down their Hatchery at their expansion. Have your scouting SCV throw down a bunker next to the expansion (but hopefully in range to pick off units that leave his base as well) and put your Reapers inside if he's building the Hatchery. Reapers are capable of lobbing explosives right out of the ports of the Bunker, and you will force the Hatchery to be cancelled or destroyed more than likely. Keep your SCV close at hand as the Zerg will likely try and break this in short order, and keeping the Bunker repaired will thwart an early breakout no problem. Once an initial attempt fails, expect several Roaches for the 2nd effort and prepare accordingly. Your tech lab can now produce straight Marauders and rally to behind the Bunker. Enjoy your victory, more than likely!
With a Protoss opponent, the Reaper Rush can last until a Stalker is in the field. Micromanage carefully and gun down as many workers as possible, and if the opportunity presents itself, take out a chasing Zealot with some hit and run tactics. Never have your Reapers engage in a fair fight! These units are frail, fragile, and futile to use as combat units in a shoot-out. When a Stalker is out, you should probably retreat and cut your losses. Put your Reapers at high ground around your opponent's base and wait for an opportunity to strike again. You'll likely only have one or two real opportunities to strike beyond the initial attack, and even then they are quickly thwarted by Warp Gates bringing in Stalker reinforcements. The same thing applies to a Terran opponent--don't bother once a Marauder is out. Once that slow finishes researching, your Reapers are fodder. Save them for scouting and another attempt later on.
Mid-Late Game - Don't bother with these. You just don't get enough bang for your buck, and expansion raiding is cheaper and more efficient with Medievac drops of the above combat infantry since they can use Stimpacks to chase down and kill workers just as fast.
No longer as specialized as before, Ghosts are now a threat in any matchup, but are especially menacing versus Protoss.
Cost - 150 Minerals, 150 Gas, 2 Supply
Build Time - 45 Seconds
Combat Stats - 100 HP, 0 armor, 10 damage (+10 vs. Light) per shot with +1 to each per attack upgrade, 6 range. Light, Biological, and Psionic armor types.
Can attack air or ground units. Can attack while Cloaked.
Early Game - Getting a Ghost early is generally more trouble than it's worth unless you are facing an aggressive Protoss player. The Ghost Academy itself is a hefty 150 minerals and 50 gas, and then you have to train a Ghost. This means it costs just as much as Thor to get the requirements for a Ghost and the Ghost itself out. You have to make your first Ghost count, and that all rests in your ability to EMP. EMP is the great equalizer of the Ghost, with a long range and a fairly good radius, though nerfed since its inception. EMP destroys all energy to units in the area, and 100 shields. This effectively removes the shields from the entire Protoss Army almost, and most notably the Immortal is rendered shieldless by this attack, removing its ability to reduce damage to fractions of what it was. Many early pushes center around the Immortal and its strong performance against your Marauders, and removing the shields from them gives your Marauders much more equal footing--though still not a fair fight!
Mid/Late Game - The Protoss caster-type units are the biggest threat to the Terran infantry mob by far, and landing an EMP turns them into harmless civilians or puny 6 damage turrets. Without this disable, your army will be split apart, have its damage cut by a third, and torn asunder by Psionic Storms and Feedback. Keeping a Ghost or two with your army and firing off those EMPs at critical moments will make or break your fights against a smart Protoss player that uses Sentries--and they all do at this point.
Researching Cloak is generally unnecessary. Ghosts are tough enough and have enough range to not be picked off very easily, and after they unleash their EMP, their job is more or less complete. If you miss some Templar with the EMP, you might be in a quick-draw showdown of micromanagement to see which player can instant kill the other faster--if you can Snipe the Templar in time, or if they can Feedback you in time. Feedback sports an impressive range of 9, so the Protoss player will have the advantage unless they have their Sentries selected first. Typically Protoss players Forcefield first, Psi Storm second, so you have that period of vulnerability. All it takes is one Snipe. One shot, one kill.
The only time I'd go for Cloak personally is when going for a Nuke. Nukes are cheaper at 100 minerals and 100 gas each, and no longer require a worthless add-on to the Command Center or a silly amount of population. They take seemingly forever to fall though, and do less damage than previously to main structures--the damage cap is now 500 damage per nuke. You'll need to drop 3 in order to instagib an expansion. Nukes do have their uses, and against Zerg especially you can get things done with Nukes that are unexpected. Zerg players tend to cluster their tech and unit structures, and a pair of Nukes will render them unable to make anything beyond Drones and Overlords once more. Again, the downside to this is that you spent 300 gas on 2 ghosts, 100 gas on cloaking, and 200 gas on the nukes themselves. That's a 600 gas advantage to the Zerg, and that's 6 Mutalisks, 12 Hydralisks, or a frightening amount of Roaches or Banelings. This strike will likely trigger an instant all-in attack from the Zerg, and you need to be ready for that!
Note that EMP removes stealth from those units hit. If you're quick, you can reveal Dark Templar and kill them before they can reach you, and pick off Observers as they try to stay with your army or scout your base.