GDI Arsenal and Mass Combat
Mass Combat has a lot of preset elements. Many of these are "assumed", such as the naval elements. This list only covers notable GDI units.
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GDI in the context of the campaign typically have access to advanced weapon systems for the majority of their troops. Equipment and training for GDI troops tends to be consistent in quality across the board, with advanced weapon systems like the Mammoth Tank being the exception. In the First Tiberium War, the Global Defense Initiative relies on overwhelming firepower to defeat the Brotherhood of Nod in the field and beyond.
In terms of infantry elements, the GDI isn't very flashy. GDI Riflemen are well-trained and equipped. For anti-air and armor purposes, GDI's standard FIM-92s and AT4s aren't significantly more powerful or reliable then similar equipment fielded by the Brotherhood of Nod. GDI Combat Engineers are better equipped than their Nod counterparts, but meet their match and betters when it comes to dealing with Nod Flame Troopers and Chemical Warriors. GDI Commandos aren't very different from their Nod counterparts. Again, the equipment and training regimen may be different, but the results are the same.
Where GDI excels tactically versus Nod infantry wise is the Grenadier, a heavy support element equipped with kestrel grenade launchers. Secondly, all GDI infantry come equipped for nighttime fighting by default.
Where GDI begins to shine is in the realm of vehicles. GDI forces are largely mechanized, and aforementioned infantry units are often transported by M113 APCs. Humvees provide motor recon and light fire support to GDI forces in the field. The star of the GDI artillery force is the M270 MLRS, which is capable of delivering a devastating salvo of rockets at a range of nearly thirty miles.
The workhouse of the GDI is the M1A2 Abrams Main Battle Tank. Even with the birth of the monstrous X-66 Mammoth Tank, the M1A2 position on the battlefield remains relatively secure and capable of dealing with most armored Nod threats when massed. The Mammoth Tank, equipped with two 128mm cannons, is large enough to provide artillery support. Powered by an atomic generator, the Mammoth Tank hosts an advanced suite of computers that feed tactical data to command in real time.
The X-66 Program is controversial. Critics argue that GDI's fleet of M270s and M1A2s are more than enough to deal with Nod forces, and that a company of M270s and M1A2s can outgun an X-66 at a discount. Defenders point out that an X-66 can engage a platoon of M1A2s ten miles beyond the effective range of the M1A2's armament, and that the ability to shell Nod bases from afar with a vehicle that can sustain attacks from Nod hit-and-run tactics isn't anything to scoff at.
Moving on to air units, both GDI and Nod make use of Chinook and Hercules medium and heavy lift aircraft. For GDI, the Hercules is able to carry a single M1A2, and a pair of Hercules can carry a Mammoth Tank. GDI also makes use of Blackhawk helicopters that can insert commandos or other infantry forces behind enemy lines stealthily.
In terms of close air support, GDI makes use of the aging A-10 Thunderbolt and smaller, newer Orca Assault Craft. Both perform very well versus anything Nod field, but the Orca program is definitely on the ascent. Black Widows provide tactical air support and can duel with their Nod counterpart very well.
At sea, GDI has access to the Gunboat and Hovercraft. The Gunboat is a small ship equipped with tomahawk missiles and is invaluable for providing heavy artillery support to GDI forces on land. Hovercraft, on the other hand, can move troops and vehicles from carrier ships to beaches and provide minimal fire support. Hovercraft have the added bonus of being able to operate on land, especially in deserts or swamplands.
Finally, there are the GDI defensive structure. The Guard Tower is nothing to write home about, but the Advanced Guard Tower is a significantly powerful defensive structure. If not for GDI's Obelisk of Light, the Advanced Guard Tower would likely have been the star of military fortification enthusiasts.
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In summary, GDI doctrine is simple: Hit hard. GDI forces are well-disciplined, well-equipped, and often mechanized. Very rarely does will a GDI company be outgunned by Nod company.
The biggest drawback for the GDI is the sheer expense of most of its standard forces and the cost of supplying them. The cost of maintaining a single Mammoth Tank for a month could support 350 GDI riflemen for a month. Lower tier Nod troops are worse equipped, but make up for their lack of training and equipment with a fanatical dedication to the Brotherhood. If not for the combined economic might of most of Europe and the Western Hemisphere, GDI's war machine would grind to a halt due to lack of repairs.