Terraforming is the process of altering the environment and ecology of a planet or moon to resemble that of Earth. After the fall of the Ultor Corporation during the First Martian Revolution, the Earth Defense Force began the terraforming of Mars.
By the coming of Second Martian Revolution in 2125, the surface of the red planet was terraformed enough to provide breathable atmosphere and bearable temperatures and pressure without necessity of wearing environmental suits.
About fifty years later, the Terraformer was destroyed by Marauder Cultists led by Adam Hale, forcing the Martians to live in caves to avoid the weather-chaos that was raging on along the planet's surface. A few years later, the Plague Armageddon broke out, causing the Martians to be terrorized by an alien species in the underground caves. Darius Mason, a former Red Faction technician who had non-purposely caused the outbreak of the aliens, repaired the Terraformer, causing the aliens to die in the changing atmosphere and allowing the Martians to live on the surface once again.