Civilization Revolution begins in 4000 BC, with a lone settler in the middle of a little-explored region. That settler has the capability to found a city, which, depending on its specific mix of geographical surroundings, begins harvesting food (for the continued growth of the city), production (for the creation of units and buildings), and trade (that can be then turned into either research points or wealth).

The game is set in 2035, 20 years after the events of XCOM: Enemy Within, in a scenario in which humanity was defeated by aliens. XCOM proved incapable of attenuating the alien threat and was quickly betrayed by the council nations, who surrendered to the aliens shortly after the invasion began.

The game, set in the modern-day Earth, deals with an international response to a global alien invasion. The player assumes the role of the commander of XCOM, the most elite military and scientific organization in the history of mankind, engaged in a seemingly hopeless war against an unknown extraterrestrial enemy with far better technology and capabilities.

XCOM: Enemy Within is a stand-alone expansion pack for the strategy video game XCOM: Enemy Unknown.