Which 2010 Call of Duty title began the Black Ops sub-series?

Which 2010 Call of Duty title began the Black Ops sub-series? Call of Duty: Black Ops.

Developed by Treyarch and published by Activision, Black Ops was released worldwide in November 2010. It is the seventh main Call of Duty title and follows World at War, linking the two games through characters, events, and Treyarch’s development lineage.

Its campaign moved the series into the Cold War, with missions involving Cuba, Vietnam, Laos, the Soviet Union, and other locations. Players control CIA operative Alex Mason, whose fragmented memories drive the story. The game’s multiplayer also expanded customization with COD Points and more flexible loadouts.

A common mix-up is confusing Black Ops with World at War, which came first but is a World War II game and acts as Black Ops’ narrative predecessor. Later entries, including Black Ops II, III, 4, Cold War, 6, and 7, form the sub-series that this 2010 game introduced.