Call of Duty: Black Ops takes place during the 1960s in the Cold War. It focuses on CIA clandestine black operations carried out behind enemy lines. Missions take place in various locations around the globe such as the Ural Mountains in central Russia, Cuba, Kazakhstan, Hong Kong, Laos, Vietnam, and the Arctic circle. The single-player campaign revolves around an experimental chemical weapon codenamed "Nova-6".
Stuck and need some help? Check out some of the questions the community have asked relating to this game. If none of these answer your problem or you want to get some tips when it comes to a particular level, feel free to submit a question of your own.