Once upon a time XCOM: Enemy Within was going to be a simple add-on pack for Enemy Unknown, but it ended up adding so much to the core game that 2K opted to release it as part of a bundle that includes the main game and all the previous DLC. Enemy Unknown takes place on a modern Earth, under attack from an alien invasion. Facing an unseen enemy of clearly superior technical capabilities, Earth's governments combine to create X-COM. Playing the commander of this global force, your mission is to create an operational base, research alien technologies, organise combat missions, and control your soldiers in battle. You'll dispatch aircraft to intercept and destroy or capture UFOs, and manage ground forces in their battles with alien invaders. All of this is controlled from your XCOM base.