Now with 45 hp, the SCV is by far the weakest of the 3 races harvesters (even though it has the most HP). Being able to attack the SCV while its building makes it very susceptible to being destroyed by early harasses by your opponents scouts (usually other harvesters). To defend your builders (very early game) from harassment, pull an additional worker or 2 to chase the enemy harvester. If they get your builder too low on life, cancel him off the building (the new hotkey is T), and get a new builder on there immediately.

SCVs can be both repaired and healed by medivacs.

- Always drop mules at the highest qty resource available- what I mean is don’t drop a mule on a mineral that has only 400 mineral points remaining if there is one available to you with 1000 mineral points remaining. This will keep your workers harvesting efficiently and not unnecessarily reduce the number of mineral patches available to harvest from.
- Some neat tricks with mule drops:
o If you see banelings coming to blow up a wall on your base (or going at a group of marines) drop a mule infront of them to soak up some of the damage. Technichally this is costly, (~250 minerals that would be mined by the mule), but often keeping your army (or your base) alive is more important than the minerals mined from the mule. This can be a game winning play if you drop it at just the right moment.

o The same trick can be used to take the opening shot of a siege tank so you can move your army in safely to kill it. 

The Terran’s lowest tech unit, the marine is a versatile unit that can and should be used all game, every game as one of your primary army units. The marine’s strength is in numbers, and cost to dps ratio is quite high. They are the only tier 1.0 unit that can attack air, and get awesome upgrades with combat shield, and stim pack. However, the marines are squishy, and fall quickly to any concentrated fire or fire from units with splash damage (hellions, siege tanks, banelings and colossi all ravage marines easily). The marine; while strong on its own, needs to be supporting / supported by your other army units. Points for marines:

- Don’t leave them in the front: Marines are best suited to be positioned behind your higher tech, more HP units (ESPECIALLY MARAUDERS!). Don’t put them in the front where they will die before they can do their damage.

- Getting combat shield is important- +10 hp is an additional 22% hp for your marines. Get this upgrade any game where you plan on building marines all game long.
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- Use stim pack sparingly- Try to use stim packs only when actively engaging your opponents- Marines low overall hp should force you to be stingy with your stimpacks until you have a few medivacs hovering overhead.
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- Mid game, or any time you are turtleing, spread your marines throughout your bases in order to make yourself difficut to harass. You would be surprised at how quickly a few marines kill a dropship, overlord, or mutalisk.
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- Marines make excellent backup for nearly every other terran unit, and they should be used nearly every game in quantity.
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- Due to their low damage, +atk upgrades are a must for later in the game, because high armor units will just ignore the marines otherwise (a fully upgraded ultralisk would take 1 damage a shot from an un-upgraded marine).
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- Banelings are really- really good at killing marines in groups. If you do not have stimpack, you cannot reliably run from them. Focus firing them does not work because they explode upon death. Key is to micro your marauders (or thors if its that late in the game) straight into the path of the banelings . It will cost the zerg player as much as 8 banelings depending on upgrades to get through a single marauder.

The marauder is a member of the new unit class for SC2- the Tank. His job is to soak damage- and he does this very well. Marauders should always be the meatshield for your army (if you are bio based, that is). That isn’t to say that he doesn’t do damage, he does (exceptional damage to armored), but you still want him on the front lines to be soaking hits for your much higher DPS marines / siege tanks. With the concussive shells + stim pack, the marauder can kite units better than any other unit in the game, and any time you have a numerical advantage your opponent is in for heavy losses.

O how I love the reaper. Definitely my favorite unit from all 3 races to come out in SC2. Its fast, has paper thin armor, is super maneuverable, and does ridiculous damage to light units and buildings. I have won the game with a single reaper before, but have also lost games from overproducing them. Their absurdly high gas cost (50/50) prevents you from teching AT ALL if building this unit in any kind of numbers, but that shouldn’t deter you from using them. They make excellent scouts all game, and if micro’d properly are basically unkillable, save for running into a Stalker with blink. All that being said, however, they do not hold their own in a standup fight, and because of this are basically useless on certain maps (Steppes of War, and to a lesser degree, Scrap Station), where access to the back of your opponents base is limited, (even with cliff jumping). Here are a few ways to use the reaper properly (Please note that the following bullets apply only if you want to use reapers in that game… I know its obvious but some people are thick ):

- Set your build order so that you can get the reapers as soon as possible, as the earlier they get out the more effective they are. The most common (and efficient) build order for fast reapers is : 10 Rax 10 Gas 11 Supply 12 Tech Lab 12 Orbital Command. This build does not cut production by very much and allows reapers in your opponent’s base well before the 4 minute mark. The reapers getting to their base early will also alert you of any fast teching being done, and will give you time to prepare for any style of attack your opponent could mount.

- Try to micro each reaper independently. They are much more effective solo than in groups, especially until you get their speed upgrade. On Desert Oasis, you can be bouncing up and down the cliff behind their mineral line with impunity against zerg and protoss, as long as you have each reaper going up and down at different areas, forcing their units to chase you (probably with little success).

- Zerg’s who fast expo (15 hatch, or 14 pool 14 hatch) will lose every game to a 2 rax reaper build when micro’d properly. From all my experience, there only options for defending the FE from reapers early is to pull their queen from their main, and stop drone production in favor of zerglings. If you force this behavior, you are already at an economic advantage. In addition, they pull their defenses to their expo, you can easily begin running from expo to main and back to harass the harvester line, which will force them to make some static defenses, further damaging their economy. This seems to have become even better with reaper nitro packs being 50/50 upgrade. You can successfully mass reapers vs a FE zerg as long as you keep an eye on their tech buildings. If they get roaches you need to stop reaper production and switch to marauders. If they tech lair, get a factory and a engineering bay. Spire, get turrets and a thor, hydra den / infestors, get reactor'd hellions and marauders.

- The hardest part about using reapers is maintaining macro while microing the reapers. Make shore your barracks and at least 1 scv for building are hotkeyed, so you can maintain production while harassing your opponents. This is EXTREAMLY important, as failing to build while destroying your opponent’s harvesting nets you no advantage whatsoever.

- Players catch on quickly to reaper harasses and set up defenses accordingly, so as soon as you feel that your reapers aren’t going to be able to do cost effective damage, pull any living ones you have left to the xel’naga towers on the maps, and use them as scouts for the duration of their lives. If you have 3+ reapers still alive at that point, make sure to keep them busy scouting, and use them to back door your opponent and punish them if they attack you, or as either a diversionary attack at an expo when your main army wants to push on their main. They are extremely useful for this purpose alone, but probably not worth the investment if you weren’t harassing with them early.



Links to other threads involving reapers:
[h] holding off super fast reaper
The new reaper terrans- how?

The ghost is a combat support caster with decent HP, good damage, and powerful abilities. Used properly, the ghost can be a powerful addition to any army composition against any race, or can be used as a solo harasser to attack mineral lines (with the powerful +10 damage to light), and calldown nuclear strikes where necessary. EMP is essential vs a protoss army with immortals, sentries, or high templar, and is seeing use against terran as a way to reveal cloaked banshees, nullify ravens, and stop medivacs from performing their duties. While you can EMP an infestor to stop its use as well, the ghost’s energy is better used to Snipe zerg units (like the infestor!). Snipe deals good damage at long range with no reduction from armor, so shift-queing sniping down priority targets is being used more and more often to punish the swarm. 
Cloak can be used effectively if researched early to harass mineral lines, or just make the ghost harder for your opponents to spot in an important battle. This is extreamly important mid-lategame vs protoss who are using high templar against you. Getting an EMP off from a cloaked ghost on their high templar before the fight kicks into high gear will win many games.

The hellion is quickly becoming a new favorite of mine, even though it is tough to use properly. The hellion can be a vicious, harvester crushing machine if micro’d properly, and can even hold its own in standard combat vs light armored units. Fast hellion builds can be wickedly powerful, and hellion drop harass is becoming a common sight on the ladder. The hellion is extreamly fast, does damage in a line, so it can hit multiple targets at once, and gets a huge damage bonus to light. The damage to light can be further increased by researching infernal pre-igniters . Before the upgrade, it will take 3 shots to kill a drone/scv/probe (16x 3 = 48 damage would kill all 3, even if they had an armor upgrade), and after the upgrade it would take 2 shots to kill a drone / scv / probe ( 24 x 2 = 48). This means without the igniter upgrade, your harass should have a minimum of 3 hellions (so you can 1 shot probes), and with the igniter upgrade you should have at least 2 hellions for your harass. Since hellions cost no gas, they are a great unit to use in addition to a higher tech army. Because of their speed, they are invaluable as scouts as well. Additional hellion tactics:

Multi-base split- 
When your opponent is on multiple (3+ bases), send a small # of hellions to each base, and send your main army at their main. If you can fight their main army to a stalemate (you both destroy most of eachother’s force), or even just hold them in their base for a short time, your hellions should be able to cause enough damage to their economy to allow you to pull ahead in the macro race.

Side /Flanking attacks:
Hellions in standard combat should always flank the enemy units, or come in at the sides. They deal damage in a line so putting them on the sides of your opponent’s army will increase their damage threefold. You should flank them instead if they have less army than you, and you want to trap their units and force them to fight.

The siege tank is the iconic terran unit, and when used properly can devastate your opponents, both on offense and defense. In siege mode, the siege tank has the longest range of any unit in the game, and does a massive amount of damage with splash. This makes it ideal for defending your base, and also for assaulting (or even just harassing) your opponents. Siege tanks are, however, expensive. 150/125 and 3 supply is a hefty cost for a single unit. However, when you consider the damage potential and strategic advantage of the siege tank, the cost is justified. Siege tanks also do well when not in siege mode vs immortals, roaches, marauders, other siege tanks, and thors. 

Strategic defensive placement:



Strategic offensive placements:



Walking siege tanks:

Now with better pathing! The new Thor (post patch 11) is a much different beast that the one we were originally introduced to. Smaller, faster firing with less damage, and less effective vs heavy armor air, the Thor is still a force to be reckoned with. Their ability to attack both ground and air, their relatively high hitpoints, and their special attack ability make them a great all around unit, useful in almost any situation against any race. Always make sure to repair Thors if possible, as their greatest weakness is their vulnerability to focus fire. Thors should not be a stand alone unit (although the single thor drop is still devastating, and the early Thor push still can work...) and should be backed up by units that can deal with a number of small targets. The Thor makes short work of most ground units, and the 150mm cannons turns ultralisks, immortals, colossi, and opposing thors into expensive meatpiles. In addition, Thors can be used to defend expansions from flying harass. One Thor will deter a large # of mutalisks because of the splash damage, and can even fight off void rays if being repaired.

The Viking is both an air superiority figher, and a mech capable of dealing solid damage on the ground. Cost for cost, the Viking has to be one of the best (most versatile) units in the game. Capable of harassing, scouting, spotting, and not outmatched in a stand up fight with anything at its cost (will 1v1 a hydralisk, won’t lose terribly to a stalker). The Vikings massive range with air makes it ideal for sniping out priority targets (colossi, ravens, broodlords, battlecruisers, carriers, and the mothership), as well as for sniping overlords. I often have been making Vikings as a primary unit, and being able to double build them with a reactor allows me to produce them in quantity relatively early in the game. Their high mobility also allows them to harass and be back on defense in a relatively short time. In combination with siege tanks, Vikings can allow for a really tight defense while still making attacking runs on your opponents. 

Medivacs are a combination unit, both a healing caster and a shuttle in one. They are important for any bio-based army as support, and can allow a terran player the mobility he needs for harassing and generally moving about the map. Dropship tactics have been around since SC1, and haven’t changed much in sc2. You can use nearly every single terran unit in dropship harass, and harassing with marines /marauders has become extremely effective given that your dropship heals them.
under construction 

Banshees are cloakable gunships that do impressive DPS to ground units, and have the body (hitpoints) of a siege tank. However, they are expensive, slow to build and slow to move. The fact that they can cloak makes them perfect for harass, however they fare equally well in standard combat. Mixed in with a regular army, they are a great addition, especially vs protoss and terran. It is important to note, that if harassing, it takes 2 shots to kill a probe / scv / drone (do not focus fire with 3 or more banshees on harvesters). Banshees can take down a stalker or hydralisk 1v1, but since they cannot attack air they should fear any air unit. Either escort them with Vikings, or expect to lose them if you are going to harass. 

Ravens are Terran’s new mobile detector unit, however this unit has much, much more utility than just being able to see invisible. Ravens have the potential to do whatever task you need them to do, from harassing opponent expos, to doing massive damage mid battle, and even protecting your army from death.

Point Defense Drone
Probably the most underused ability in sc2, the PDD can single handedly turn a battle in your favor. If your opponent has only projectile attacking units (Vikings, hydralisks, stalkers), this little robot will give your team a few seconds of uninterrupted killing, and that is usually all you need when you have a large group of marines / marauders. I highly recommend using this ability as often as you can.

Auto-Turret
Can be used both offensively and defensively, the auto turret is best used to harass expos and defend yourself from banelings and other melee range units. You can drop down a line of ATs infront of your army to soak damage from basically any attackers, while providing additional DPS on top of that!

Seeker Missile
While the energy requirement is outrageous, this ability can’t be counted out. 100 AoE damage is A LOT, and throwing 3 or 4 of these into your opponents army can be devastating, especially to low hp units like marines and hydralisks. Also, these can be used as a deterrent when thrown at fast units like mutalisks. Inevitably they will run away from the missiles, granting you the time you need to throw down a few turrets or have those Vikings finish building. Be careful, however, as the splash damage isn’t limited to your opponents forces.

The BC is the biggest, most expensive unit in the terran arsenal, and it performs as such. It has a thick hide (3 armor and a ton of HP), does ridiculous damage, and has a long-range 300 damage snipe shot with yamato gun. It can be used effectively to defend a large area, and is no slouch on offense either. In a long, drawn out game, BCs are at their prime, but with their prohibitive costs, however, I would only opt for battlecruisers once I have secured a third base. 

Yamato gun is an absurdly powerful ability and should always be researched if battlecruisers are going to be built. +Atk upgrades are also a must, and armor upgrades are always nice.

Battlecruisers should be supported by the entire terran arsenal, and are not a unit that should be massed. (in a 1v1).