GDI is a powerful army that can be great in either late or early game.
It has no real weaknesses in any point in a fight and can crush
opponents with their advanced technology and powerful units. Although
not as advanced as the Scrin, GDI can hold up against nearly anything
and its units have plenty of armor to back them up.  Their units are
more expensive then Nod's but they are also more powerful.

GDI Units

Rifleman Squad
Rating: **
Abilities: Dig a fox hole, Call for Transport.
Upgrades: Composite Armor
Summary: They are very weak to almost every unit in the game except the
rocket infantry and the other rifle infantry.  The only real use for
these is to counter early infantry rushes and scouting.  The reason
these get a two star rating is because the fox hole ability and their
ability to be upgraded.  With the upgrade they are still very weak
though.  You should almost never have to use these guys unless you need
a cheap counter to other infantry units.  The fox hole ability is quite
useful in campaign and also in very rare circumstances in multiplayer
where you need a defense structure that uses no power or you lost all
ability to build structures.

Missile Squad
Rating: ***
Abilities: Call for Transport
Upgrades: Composite Armor
Summary: Only useful against early game tank rushes, cheap anti air,
taking down walker units, and to put in an APC.  These are very weak,
but very useful as a cheap unit to back up your early game forces.
Never use these in mass against any air units except the Orca and
Firehawk.  Your money is better spent building other anti air vehicles
and structures because most air units rip infantry to shreds really
quickly.  Always remember to garrison them against tanks when possible
and if that is not possible, make sure to micromanage them to make sure
they don't get ran over.  This unit can be used in mass to take down
walker units easily.  Followed up by an engineer, this can be very
useful, cheap, and effective.

Engineer
Rating: *****
Abilities: Call for Transport
Summary:  These are the most useful early game infantry. They can be
used to capture buildings which can turn the tides of any battle very
quickly. Even during late game, these infantry are still used proving
they deserve the five star rating. These can be a commander's worst
nightmare if caught running into a base that is undefended.  Just
remember, these guys are very slow and the weakest unit in the game so
protect them if possible. Load them up in APCs and you can engineer
rush them unlike any of the other factions in the game. Also, don't
forget they can repair bridges, your structures, and resurrect fallen
walkers.  They cannot repair garrisonable buildings as in the past
games though.

Grenadier Squad
Rating: ***
Abilities: Call for Transport
Upgrades: Composite Armor
Requirements: Command Post
Summary: These guys would be more useful if infantry were more common
in the game.  As it stands right now, Grenadier Squads are semi-useful
against vehicles but they really shine as another superior anti
infantry unit. Their grenades kill almost any infantry in one hit, and
clear out garrisonable buildings with ease.  In urban combat areas,
load one into an APC and start the rampage.  They will clear an entire
city in seconds, reducing enemy infantry to bits and pieces.

Sniper Team
Rating: ****
Abilities: Call for Transport
Requirements: Armory
Summary: These guys kill infantry in nothing flat. They are useful to
have around to keep pesky Engineers, Commandos, and Shadow Teams away
from your base.  They have stealth capabilities and the ability to spot
targets for Juggernauts. What more could you want from an anti infantry
unit? Nothing really, except for the fact that you hardly ever see
enough infantry in this game to build more then a couple of them.
Their ability to spot for Juggernauts is great, except it can be tough
to get close enough to an enemies base without getting detected with
all the stealth detection in this game.  To use their ability to spot
for Juggernauts, you simply move the sniper within sight of the target
and then go to your Juggernauts and click the Bombard Target button.

Commando
Rating: **
Abilities: Jump Jets and Call for Transport
Requirements: Armory and Tech Center
Summary: This unit is basically a waste of money. The only use of this
infantry is to sneak into an enemy base and blow some stuff up.
Although it is great against infantry and walkers, there are a lot
better units that are more useful to take those down. I guess if you
ever see an undefended side of a base you might be able to do a little
damage.  Don't expect to do much because this unit is easily countered
by a simple anti infantry turret or two.  It's a nice unit, but other
units tend to be better for the job then this guy.

Zone Trooper
Rating: ****
Abilities: Jump Jets, Call for Transport
Upgrades: Scanner Packs, Power Packs
Requirements: Tech Center
Summary: These guys are the best late game infantry the GDI have. Their
only true weakness is air, but with a couple of Mammoths backing these
guys up, they are pretty much unstoppable against anything short of a
Sniper Team or Shadow Team.  They can easily do more damage then a
Commando if they find a cliff or river to Jump Jet across and they can
do damage faster.  Their armor is superior for infantry units, and
their rail guns can pierce through even the heaviest of armor.  When
upgraded, they have the ability to regenerate health while idle and
detect stealth units.  Basically, these guys are the infantry you want
to be using at all times once you tech up to them.

Pitbull
Rating: ***
Upgrades: Mortars
Summary: This is the fast recon/anti air unit the GDI has.  It works
wonders against aircraft (except Scrin's heavy aircraft) because of its
speed and power.  These can easily be destroyed so don't use them
versus Scrin's heavy aircraft, instead use other aircraft.  If your
base is getting assaulted with air units, this is a great unit that is
cheap and fast to build.  Other then scouting and anti air, it also has
one more advantage, which is stealth detection.  Early game these are
great against Shadow Teams.  Besides the uses mentioned before, there
is not much reason to build these in mass.  A couple around the base
will do quite nicely and other then that, these are horrible at
assaulting the enemy.  Since it has quite a bit of speed, it can be
used to effectively run over enemy infantry.

Predator Tank
Rating: ****
Upgrades: Railguns
Summary:  The main battle tank of the GDI is also the most powerful
light tank in the game.  With its railgun upgrade, it can easily punch
a hole in a base against light defenses and armor.  The downside to
this is that they are not very good against late game units.  Use these
if you plan on tank rushing early game, or if you just need a cheap
diversion late game.  Although these cost more then the other light
tanks, they are a lot stronger and more durable.  Also remember to run
over any infantry you see, they don't stand a chance against a tank of
this size.

APC
Rating: ** (without infantry) **** (with infantry)
Abilities: Lay Minefield
Summary: Without any infantry on board, this unit is more or less a
waste of time. Early game it's not bad at taking out infantry, but even
then I would prefer using a Predator and just crushing infantry.  It
can also take on air units out even though a Pitbull does that job much
more effectively.  As for with infantry, this unit can pack a serious
punch.  Rocket infantry are the most effective overall to put in here.
This makes the cost at exactly that of one Predator tank except that
it's good against any unit.  Other infantry such as Engineers are also
very useful to put in one and then rush the enemy base.  Zone Troopers
also make this unit pack a serious punch with hit and run capabilities.
A great unit if infantry are placed inside, otherwise this is just a
below average unit. Also, their minefield ability is nice to deploy at
choke points because most of the time it will kill several units before
the mines are used up.

Harvester
Rating: *****
Requirements: Refinery
Summary:  Just another harvesting unit from the past games. These are
vital to your economy so protect them at all costs.  GDI's harvesting
unit happens to have an anti infantry weapon attached.  It is kind of
useless since it could just run over infantry anyways, but it does help
protect your harvester so I can't really complain.

MCV
Rating: *****
Summary: Deploys into another Construction Yard. Great for base rushing
and to have another one handy in case yours happens to get destroyed.

Rig
Rating: ***
Requirements: Command Post
Summary:  This is a great unit to send along with your troops to repair
them during battle.  Another great use is for an expensive defense that
uses no power and can repair you units.  These used with a Surveyor can
create expansion bases that are immediately defended. These should
never be used in mass and just one in an area holds that ground very
effectively.

Mammoth Tank
Rating: *****
Upgrades: Railguns
Requirements: Tech Center
Summary:  This is the mother of all tanks.  It can hit both ground and
air targets and has TONS of armor.  The Mammoth is awfully slow so be
prepared to take a few casualties just on the way to the enemies base.
This tank is effective against everything in the game even infantry.
Spamming them late game is often all people will do because of their
might.  These combined with Zone Troopers make a VERY effective late
game assault force that can take on even the heaviest of armor or
defenses. Be sure to research the railgun upgrade as soon as you start
building them because it increases their power against all ground units
by a large margin.  If you spam any ground unit in the game, this is by
far the best one.  Some go so far as to say people are noobs when they
spam them because "they take no skill."  This is very true, unless he
also has other units supporting them.

Juggernaut
Rating: ***
Abilities: Bombard Target
Requirements: Tech Center
Summary:  This is a great unit to support your main forces with. These
walkers are very slow and not heavily armored so remember to defend
them.  Combined with a sniper, they can fire bomb something from
anywhere on the map.  Unfortunately the hard part is actually getting
the Snipers to the enemy's base without having them get killed.
Building a couple of these and having them behind your main forces can
really help if the enemy is heavily defended. Finally, they also leave
walker husks so if they do get destroyed simply capture the husk with
an Engineer.

Surveyor
Rating: **
Summary:  These are slow, very weak, and defenseless.  Most of the time
you only need to build one or two at the beginning to make expansion
bases at the other Tiberium fields.  Other then that, these are
horrible at rushing someone unless they can remain unseen.  They take
20-30 seconds to deploy so be sure to defend them.

Orca
Rating: **
Abilities: Deploy Sensor Pod, Pulse Scan
Upgrades: Sensor Pods
Summary:  Orcas are considerably less effective then other light
aircraft.  The only thing that they can do better then Firehawks is
take out vehicles.  These tend to be very weak to anti air and are slow
to unload their missiles.  Orcas are very useful early game when your
enemy might leave his harvesters open for attack.  Also they can be
used to stop incoming tanks and walkers effectively.  Because it takes
so long to unload their missiles, you should almost never bomb enemy
bases with them unless they are undefended.  If they had a lot more
armor Orcas might be useful, but since they are easy to take down, use
Firehawks instead.  Orcas also have the added ability to detect stealth
and drop sensor pods on enemy units and structures once upgraded.

Firehawk
Rating: ****
Abilites: Missile Loadout, Bomb Loadout
Upgrades: Stratofighter Booster
Requirements: Tech Center
Summary:  Firehawks are the best units in the game for taking out a
super weapon.  The reason I say that, is because with the Stratofighter
Booster upgrade then can actually teleport instantly across the map and
then bomb their target.  Unfortunately this has a cool down so there
won't be any coming back if you enemy has plenty of anti air.  They can
also be loaded with anti air missiles at the Airfield for free.  Be
sure to make 8 or so as an emergency attack force against heavy armor
and super weapons.

GDI Structures

Construction Yard
Summary: Used to start your base. It can be undeployed and sent over to
the enemy's base to rush him.  If you are planning to do this, you
should build a Power Plant or Crane first.  This building also controls
your radar, so if you lose it you won't have any radar.  Remember to
protect this at all costs.

Power Plant
Summary:  Supplies power to your base. It can also be used to build a
string of buildings to your enemy's base.  Don't forget to upgrade them
once you get your Tech Center up.

Crane
Summary: Provides you with an additional structure build tab.  You
should always have one handy.

Refinery
Summary: This building is the heart of your economy and its Harvesters
supply it with plenty of Tiberium. Building an extra Refinery and then
selling it once the harvester appears is a good way to get a free
scouting unit and a Harvester early in the game.  Using this method
does not cost additional cash though.  In fact this gives you 1 free
infantry unit every time you do it.  Only build one per Tiberium field
and keep 2-3 Harvesters per Refinery at all times.  Remember to protect
these otherwise you might find your self with no money if your enemy
keeps destroying them.  Also Refineries increase your maximum reserve
of cash.

Barracks
Summary: Builds infantry units. Additional Barracks provide an
additional infantry build tab.

Armory
Summary: Advanced infantry technology building.  Also it can heal your
infantry that you send in.

War Factory
Summary:  Builds vehicle units (except the Surveyor, which is made in
the Construction Yard.  Additional War Factories provide additional
vehicle build tabs.  Make sure if you are spamming vehicles to build
multiple of them.

Command Post
Summary: The lesser technology building that is a requirement to build
late game units and structures.

Tech Center
Summary:  The greater technology building that allows for the most
advanced units and structures the GDI has to be built.

Airfield
Summary:  Builds aircraft units. Additional Airfields provide
additional landing pads and aircraft build tabs.  Each Airfield has 4
landing pads that hold one Orca or Firehawk each.

Space Command Uplink
Summary: Allows the GDI to use Shockwave Artillery and call for Zone
Troopers.  This is not a requirement for units or structures to be
built.

Watchtower
Summary:  The anti infantry defense tower.  Great against infantry,
useless against anything else.

Guardian Cannon
Summary:  The anti tank defense cannon.  Only useful against light
vehicles.

AA Battery
Summary:  The only anti air defense structure GDI has.  Useful against
all aircraft and make sure to keep some at your base at all times.

Tiberium Silo
Summary: Increases your maximum reserve of cash by about 2000 per silo
built. Make sure to build these if you are stock piling money otherwise
your Harvesters will stop until you spend some money.

Sonic Emitter
Summary: This is the ultimate ground defense system GDI has.  It can
pierce multiple targets and continues until it cannot go any further.
It is slow to reach its target and can be avoided by fast units so back
these up.  Against massive armies these are the most effective defense
in the game.

Ion Cannon Control
Summary:  The GDI super weapon that once built will start a countdown
until it is ready.  Keep it well defended and use it to put a giant
hole in the enemy's base.  Useful for ending matches that seem to have
no end.  Don't worry about others opinions about them, build one if
your enemy is being a turtle otherwise the game goes on forever.

GDI Support Powers

Radar Scan
Deployed from: Command Post
Summary: Allows you to reveal the shroud anywhere on the map.  Useful
to reveal the shroud to use other powers or to spy on the enemy

GDI Airborne
Deployed from: Armory
Summary: Several GDI Rifleman Squads and Missile Squads are delivered
by air as veterans.  Probably the worst support power there is.  Being
only useful when combined with the Bloodhounds power to give your APCs
some rocket infantry.

Sharpshooter Team
Deployed from: Tech Center
Summary: Drops a few Sniper Teams on the battlefield as veterans.
Useful to put snipers near the enemy base for Juggernauts to bomb.  It
is also useful if you see hordes of infantry being sent to your base or
if you have a loose Commando running around your base.

Orca Strike
Deployed from: Airfield
Summary: A few Orcas bomb the target.  Relatively weak, but it is cheap
and can be used to finish off something you didn't kill.

Bloodhounds
Deployed from: Airfield
Summary:  Some Pitbulls and APCs are deployed as veterans at the
target.  When used in conjunction with GDI Airborne, this can be used
to deploy an assault force anywhere on the map.

Zone Trooper Drop Pods
Deployed from: Space Command Uplink
Summary:  A few squads of Zone Troopers as veterans come crashed down
in drop pods.  Very useful to attack anywhere in the battlefield
because it sends them to the target almost instantaneously.

Shockwave Artillery
Deployed from: Space Command Uplink
Summary: Bombs the target with weak EMP artillery.  Very useful to stop
late game assaults because it disables anything it hits.

Ion Cannon
Deployed from: Ion Cannon Control
Summary: A massive ion cannon burst is unleashed wherever you please.
This will easily destroy anything in the radius except for a
Construction Yard.