There are 3 factions in Command & Conquer 3. Both GDI and Nod are both back to continue the war. Once the player has completed the GDI and Nod campaigns, a mysterious third Alien faction, the Scrin will be unlocked. Here is summary of the three factions in C&C 3.
Global Defense Initiative
The Global Defense Initiative’s internal structure and organization is quite similar to a supranational and large-scale integration of all of the world’s major modern day conventional armies into a single globalized military force. GDI is capable of instantly deploying vast quantities of well-trained and well-equipped soldiers backed by powerful ground, air and naval assets to any point on the globe, and this in ways that are considerably more organized, advanced, as well as on a much greater scale than any conventional real-life military force of today possibly could. Global Defense Initiative troops utilize both superior armour and fire-power, making them typically much more powerful than Nod forces in direct open confrontations, but also more cumbersome and less flexible, the exploitation of which the Brotherhood is notoriously adept at through its combinations of futuristic guerilla warfare with uniquely advanced Tiberium-based technologies. By the year of 2047, GDI forces were restructured to allow for decentralized operations in multiple theatres of war, through the establishment of forward-operating bases in all types of terrain and the deployment of specialized, reliable, and cost-effective ground and air forces supported by the most advanced network of orbital artillery satellites in history.
Brotherhood of Nod
The Brotherhood of Nod is a mysterious, enigmatic and highly militant cult of an allegedly ancient origin, which in modern times began to show the combined characteristics of a religious movement, a multinational corporation and a nation-state, whilst being none of the three in itself. The globalized brotherhood is led by a mysterious man who is known only as Kane, and its influence in the world at the advent of the events in which Command & Conquer 3: Tiberium Wars will take place eventually reached nothing short of the status of an unconventional superpower. The Brotherhood of Nod represents a flexible, elusive and worldwide cultist army which thrives on the synergy between low-tech guerilla warfare and highly-trained forces equipped with state-of-the-art communications gear and the most advanced weapon systems available, which all have been derived from the Brotherhood its uniquely adept understanding of Tiberium-based military technologies. Nod’s tactics are highly radical and appear more cruel than GDI’s, often showing little to no regard for human life, and their fascination with Tiberium also leads them to use the dangerous and toxic substance offensively whenever possible. Nod forces are completely dedicated to Kane and the Brotherhood’s cause, and are well known to fight and willingly die for either.
Scrin
The December 2006 issue of the Games for Windows magazine confirmed that the mysterious third side will be an extra-terrestrial species, the units and structures of which feature a distinct insect-like appearance. Additionally, in FMV trailer footage Kane himself is heard to refer to them as “the Visitors”, and is seen to become enraged when he learns his General Kilian Qatar considers the alien species to be a greater threat to Nod than even the GDI. In-game trailer footage narrated by C&C 3 associate producer Jim Vessella has confirmed the existence of a number of specific units, including but not limited to the ‘Stormrider’ light attack fighter, the ‘Annihilator Tripod’ (a mech unit with three laser turrets), and the so-called ‘Buzzers’ (a swarming anti-infantry unit made of razor blades). Interviews of game producer Amer Ajami additionally revealed that this alien species will feature numerous economic advantages over the traditional two factions, as well as a significantly higher build rate for both their infantry and their vehicle units, yet at the cost of having a relatively weaker protection from enemy attacks in comparison to their counterparts of the GDI and Nod factions. An IGN preview has with regards to the storyline stated that an alien mothership has been dormant on the edge of the solar system for a thousand years, in wait for a Tiberium related signal. Awakening from their slumber, the alien faction joins the fray in the Third Tiberium War with unknown motivations and goals. By February 2007 this Alien Faction would become known as The Scrin.