The Steel Talons are the “brute force” sub-faction of GDI, emphasizing vehicle power over infantry and aircraft. As such, the Steel Talons cannot build advanced infantry besides grenadiers or research the stratofighter upgrade.
Units
TitanThe Steel Talon standard combat vehicle is the Titan, replacing the predator tank. Titans are slower, but far more heavily armed and armored. Upgrading these units with adaptive armor is a must if you want to keep them protected from EMP attacks!
WolverineWolverines are a new, fast, walker unit that can scout enemy forces and shred infantry with its mounted chain guns. The perfect matching unit for the Titan, the Wolverine can be upgraded with Armor Piercing Ammunition to further compliment armor assaults.
Combat EngineerSteel Talon Engineers are combat capable, although they do little damage that they are only good against enemy engineers. Something to note is that opponents can now tell when a Combat Engineer is inside an APC (or Mobile Repair Transport) because they shoot out of them, unless it is disabled via stances.
Heavy HarvesterThe Steel Talon Harvester is equipped with a bunker that infantry can garrison. This can give you a decisive edge when both your and your opponent expand to the same field.
Mobile Repair TransportThe Mobile Repair Transport replaces the APC for the Steel Talons. While it no longer has a machine gun, the MRT can repair nearby vehicles with its accompanying repair drone. Infantry can still fire out of the MRT.

SlingshotThis hovercraft is a sole anti-air vehicle. It tears any and all aircraft to shreds within seconds, although it’s very weak in direct combat.

HammerheadHammerheads are probably the toughest air-craft GDI can build and is great against infantry. They can be garrisoned with infantry units for added versatility. Hammerheads never have to return to the airfield to reload or refuel, and you aren’t limited in the number you can build per airfield.

BehemothBehemoths are Juggernauts upgraded with built-in garrisons. Put snipers in them to counter enemy rocket infantry, or rockets infantry to add anti-air cover.

MARVGDI’s epic unit. Armed with a tri-barreled gun that fires sonic shells, this beast can be “garrisoned” by four infantry units. When garrisoned, the infantry battalion is sacrificed and one of the MARV’s hardpoints is upgraded with the infantry’s weaponry. The MARV can also be used to harvest
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Upgrades

Armor-Piercing AmmunitionYour riflemen, hammerheads and APCs deal extra damage against enemy vehicles. This could be particularly useful for hammerheads, allowing you to harass enemy harvesters.
Adaptive ArmorThis upgrade improves the armor of your Titans, Wolverines, and Mammoths (and possibly the Behemoth/other vehicles?) as well as giving them a defense against EMP attacks (note that it cannot stop all EMP attacks, as it must recharge each time it is used). Be aware that this upgrade does reduce the firing speed of the units it affects.
Buildings

Reclamator HubThis structure is required in order to build the MARV. It can also build vehicles like a normal War Factory. Naturally, you are limited to only being able to build one of these.

Support Powers

Sonic Repulsor FieldsThis power is cheap and recharges quickly, but can only affect one building at a time. The targeted building becomes immune to engineer capture (unsure about commandos and shadow teams, but it would make sense).

Thor’s HammerThis is GDI’s new base-breaking power. Your enemy will be warned by a laser beam that precedes the attack and be able to move his units in time, so it’s mostly useful against bases.

Supersonic Air AttackCalls in several supersonic fighters that quickly eliminate all enemy aircraft within the area. It takes a couple seconds to arrive, do don’t waste it on moving air units!

Railgun AcceleratorsThis power is great for head-on vehicle battles when your units have Railguns. It increases the rate of fire of all railgun vehicles, although the affected units take damage over time and you lose your power temporarily.

Other Notes
No Snipers, Commandos, or Zone Troopers
No Stratofighter upgrade
No Sonic Emitters
Mammoths start as veteran
Cannot build Armory