Unknown - Ufo: Enemy

You recover alien corpses and technology from crash sites to develop laser and plasma weaponry.

You discover that alien technology relies on Elerium-115 , a stable heavy element not found on Earth, which becomes the most vital resource for humanity's advanced crafts and weapons.

The modern XCOM: Enemy Unknown reboots this story for a new timeline. In the timeline of XCOM 2 , it is revealed that X-COM actually lost the war early on, and the "victory" from the previous game was a simulation run in the Commander's mind while they were held captive. UFO: Enemy Unknown

Destroying the Alien Brain severs the link between the invaders and their leadership, causing the alien forces on Earth to collapse and saving humanity.

Late-game research uncovers the truth: the invasion is being orchestrated by the , a highly advanced, psionic race that has enslaved other species to serve as their military arm. Their primary base in the solar system is located in the Cydonia region of Mars. The Final Assault: Cydonia You recover alien corpses and technology from crash

Once X-COM develops the (a powerful interstellar craft), they launch a final mission to Mars.

As the Commander, you start with basic human ballistics while fighting various alien species, such as the physically frail but psionic and the brutish Mutons . The "story" is largely driven by your research: In the timeline of XCOM 2 , it

The story continues in X-COM: Terror from the Deep , where a second wave of aliens awakens from the ocean floor.