Black Ops, Black Ops 2, and Black Ops 3 are all in the same universe. The Modern Warfare series is all in the same universe. Ghosts, Advanced Warfare, Infinite Warfare, and WWII are in their own universe.

The single-player campaign features two connected storylines, with the first set from 1986 to 1989 during the final years of the First Cold War, and the other set in 2025 during a Second Cold War and rare earths trade dispute between the United States and China.