X-COM is a series of tactical video games that focus on managing a team of soldiers to combat alien invasions. Players are responsible for researching alien technology, building bases, and engaging in turn-based combat. The series is known for its strategic depth and permadeath feature, where fallen soldiers do not return. The original game, UFO: Enemy Unknown, was released in 1994 and gained a cult following. Subsequent titles, including XCOM: Enemy Unknown and XCOM 2, have modernized the gameplay while retaining the core elements of strategy and resource management. The franchise has influenced many other games in the tactical genre.