Starcraft 2 Terran Army Compositions
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In this guide to Terran army compositions, you will learn
the best units to build together to form a highly effective, synergistic Terran army.
No matter what race you are playing against, certain Terran units work best when paired together. The Medivac
synergizes with the Marine. The Marine does the damage, while the Medivac heals the Marine, allowing the Marine to
make regular use of Stimpack without eventually running out of life.
Some units go well together not just because of function but also due to cost. The Hellbat synergizes well with
the Siege Tank and Thor not only due to its function but because the Hellbat costs no vespene gas, while the Siege
Tank and Thor cost a lot of vespene gas. Most Terran armies typically include a lot of Marines, Hellions, or
Hellbats, as these units only cost minerals to produce. Terran players have a lot of extra minerals due to MULEs,
so Terran armies always make use of these three units.
There are four common categories of Terran army compositions:
Bio - Barracks-based play
Mech - Factory-based play
BioMech - Combination of Barracks and Factory units
Air (SkyTerran) - Starport-based play
Below, we will cover these four Terran army compositions in more detail.
Terran Bio Army Composition
One of the most popular ways to play Terran is via the bio composition. This Terran army composition uses
Marines as its primary constituent. Bio is very easy to play and easy to macro with since Marines do not cost any
gas. New Terran players often struggle to spend all their minerals (thanks to MULEs), but playing as bio makes it
easy since you can never have too many Marines.
In the early game, Marines are very weak. They need Combat Shields, Stimpack, and Medivac support to be
effective. Marines should always be stimmed while in combat, as this increases their movement speed and attack
speed by 50%. Medivacs can be used to perform drops with the Marines and are used to heal up the Marines due to
damage taken from Stimpack or enemy units.
Traditionally, bio also made heavy use of Marauders. Marauders are still a great unit, but they have become a
bit less popular in Heart of the Swarm now that there are more unit options available to Terran players. Many top
Terrans stick to solely Marines and Medivacs, only adding in Marauders if their opponent makes heavy use of armored
ground units like Stalkers, Siege Tanks, Ultralisks, or Roaches.
Bio has the advantage of being very mobile. Marines and Marauders with Stimpack move very quickly. Medivacs with
Ignite Afterburners are also quite fast, and can be used to quickly ferry Marines and Marauders up and down cliffs,
into an enemy's base for a drop, or for a hot pick-up to escape a losing battle.
Getting the right amount of Medivacs is important for bio and biomech Terrans. If you have too many Medivacs,
too much supply will be tied up in Medivacs and your base army will not be big enough. If you do not have enough
Medivacs, your Marines and Marauders will drain all your Medivac energy and you will not be able to heal your
units. A good number to shoot for is about 1 Medivac for every 8 Marines or 4 Marauders. This will allow your
entire army to fit inside of the Medivacs as well as provide enough healing for all of your units.
Pure bio armies are definitely not as strong as bio-mech armies in head-to-head combat. Pure bio armies are also
not particularly good at defending bases. Instead, pure bio armies rely on being able to be scooped up into
Medivacs and used in "doom drops" or even being split into multi-pronged drops, hitting several enemy locations at
It is also very easy to build up a large bio army early in the game due to the low resource cost, making bio
builds very popular with timing attacks.
Terran Mech Army Composition
With the release of Heart of the Swarm and the introduction of the Widow Mine and Hellbat, full mech builds have
become very popular in Heart of the Swarm. While Factory units were always popular in Wings of Liberty, they were
typically used in conjunction with bio units, not just on their own.
The Hellbat has changed this dynamic. The Hellbat provides Terrans with a unit that pairs well with the Siege
Tank and Thor. The Hellbat's gas-free cost, generous HP pool (relative to its cost), short range, and bonus damage
to light units makes it the perfect unit to use with the Siege Tank and Thor. The Siege Tank and Thor combination
is particularly weak versus mass Zerglings or Zealots, and the Hellbat handily counters both of these melee
The composition of a good mech player will change over time. The reason for this is that to get out a lot of
Siege Tanks and Thors, mech players will need a lot of gas. Thanks to the MULE, the Terran player will start
racking up a lot of minerals. Rather than just sit on these minerals, these excess resources should be converted
into Hellbats and Hellions. As the game goes and more vespene gas is mined, the composition can become more Siege
Tank and Thor dominate.
For support, Vikings, Medivacs, and Ravens are the primary choices for mech players. Vikings are needed to
handle the primary weakness of mech builds, which is armored air units. Just a handful of Brood Lords or Void Rays
can take down a large army of Hellbats, Siege Tanks, and Thors. While Medivacs can be used to heal Hellbats, their
primary use for a Mech Terran is to perform Hellbat or Hellion drops while the opponent is distracted with your
Ravens are a great support unit in general for mech, but typically do not make it into this army composition
until the late game due to their 200 vespene gas cost. Since gas is the limiting resource for gas, you have to
consider that the 200 vespene gas spent on a Raven could just as easily be another Thor for your army.
Despite the cost, Ravens are a great support unit for mech. Point Defense Drone offers a significant reduction
in incoming damage. The PDD works especially well with mech due to the stationary nature of Siege Tanks. Once you
set up your tank line in Siege Mode, you can place PDDs around your tanks to protect them. Seeker Missile is a
great damage-dealing ability. Auto Turret is situationally useful as well. The Auto-Turret is particularly good in
TvT, where it can be used to absorb some enemy Siege Tank fire and deal friendly-fire splash damage to those Siege
Widow Mines may be used as part of a full mech build as well, though it is not as common to use them as part of
the main army composition. Widow Mines may be used to harass the opponent or defend your bases, but heavy Widow
Mine use is not common with full mech builds. By the late game, Widow Mines are more commonly used to support bio
A lot of it the Widow Mine's use has to do with mobility. Widow Mines have a fast movement speed. With Drilling
Claws, they can burrow and unburrow very quickly. Other mech units are much slower. Siege Tanks take 4 seconds to
go into and out of Siege Mode. The Widow Mine's mobility is wasted in a Terran mech army.
Another reason the Widow Mine is not used as much in full mech compositions is that full mech already deals a
lot of splash damage. The Thor deals splash damage versus air units, Siege Tanks deal splash damage versus ground
units from range, and Hellbats deal splash damage versus ground units at melee range.
Mech players typically invest heavily in armor and weapon upgrades. Since the Terran's vehicle and ship armor
upgrades are shared, the mech player can more easily transition into a SkyTerran army composition in the very late
The major weakness of the mech army is that it is very slow. Enemy players do well not to attack mech armies
head-on, rather taking advantage of mech's clumsiness by performing drops and harassment-style attacks with air
Terran BioMech Army Composition
Perhaps the most popular Terran army composition of all is BioMech. Players opting for BioMech end up producing
both biological and Factory units.
While technically any combination of units can be used, typically BioMech uses bio as its backbone and relies on
Factory units for additional support. Upgrades tend to focus on the Infantry. Marines need Combat Shields and
Stimpack to be effective, whereas 0/0 Siege Tanks and 0/0 Widow Mines are strong all game long. If the Terran has
extra resources, Vehicle Weapons are next on the upgrade priorities list after Infantry Weapons and Armor.
As an example of an effective BioMech build, consider the Terran vs Zerg match-up. Marines and Medivacs are very
good against most Zerg army compositions. However, Marines are weak against the Baneling. By adding in a few Siege
Tanks, the Terran player can kite back to their tanks with their Marines while the Siege Tanks take out all the
Banelings, minimizing damage.
Siege Tanks are almost always used as part of BioMech builds at a minimum to help defend expansions. It is not a
big supply investment to add in a few Siege Tanks to defend the third base, but doing so significantly increases
the security of this expansion. Widow Mines are also a cheap way to defend Terran expansions, particularly if the
Terran opts for a macro CC.
The biggest question BioMech players have to answer is whether they want to use primarily Siege Tanks or Widow
Mines to support their primary force of Marines and Medivacs. Siege Tanks are overall more powerful and easier to
use than Widow Mines, but Widow Mines are cheaper and a much more mobile unit. Terrans who value the full mobility
that bio provides but who also need splash damage support against Banelings may opt to use the Widow Mine instead
of the Siege Tank.
Both the Widow Mine and Siege Tank are viable support options for the Terran player. The best Terran players
have even been able to use Widow Mines as a Siege Tank replacement against Zerg players. The Siege Tank still
predominates in TvT - its range of 13 makes it quite strong against the Widow Mine.
Against Protoss players, BioMech builds may exist without the heavy use of Widow Mines or Siege Tanks. Instead,
a few Hellbats (but not too many) may be added in to help neutralize Zealots. Since Hellbats get healed by
Medivacs, they synergize decently with bio forces. The only problem with the Hellbat is that it uses vehicle
upgrades, not infantry upgrades. With this army composition, Vikings are added to handle Colossi while Ghosts are
added to deal with High Templar and Archons.
SkyTerran Army Composition
SkyTerran is a powerful army combination consisting of an approximately equal mix of Battlecruisers, Vikings,
and Ravens. Battlecruisers are strong versus most units in Starcraft 2 thanks to Yamato Cannon, a huge HP and armor
pool, a great anti-ground and a solid anti-air DPS rating. Vikings and Ravens cover for the Battlecruiser's few
The two keys to making SkyTerran work are getting enough resources and upgrades to even execute the build along
with properly controlling the Raven. Battlecruisers and Ravens both cost a lot of gas, so making a large army that
features these two units is not very easy. It is often very late in the game by the time the Terran can afford to
make a fleet of BCs, especially if ship weapons and vehicle/ship plating have been researched to +3/3.
Simply building Battlecruisers and Vikings is not enough to make this army composition work. You need a large
amount of Ravens and you need to control them well. Ravens are used to drop Point Defense Drone. Point Defense
Drone will absorb the attacks from the three most common Battlecruiser counters: Vikings, Corruptors, and Tempests.
Additionally, Seeker Missile is very effective against packs of Vikings, Corruptors, and even ground units like the
The main problem (aside from cost) of the SkyTerran army faces its lack of mobility. Battlecruisers are very
slow. If you are on offense with a fleet of air units, the enemy player can easily go around your drop and try to
get into a base race scenario. Since Battlecruisers move slowly and Vikings and Ravens do not attack structures,
this is not ideal for the Terran player. Missile Turrets and a few well-placed Siege Tanks or Widow Mines can help
stop sneaky drop attacks from losing the game despite having superior forces.
Terran players have a lot of great army compositions available in Starcraft 2. Many top players pick a preferred
army composition and stick to it as much as possible. By playing less army compositions, it is faster and easier to
learn all the nuances of the particular units in that unit composition. It is much more time consuming and
difficult to master multiple army compositions.