https://www.eastbaytimes.com/2020/11/20/review-call-of-duty-black-ops-cold-war-treads-familiar-path/

Although the “Call of Duty” seems like a monolithic franchise, it actually contains different eras and subseries. The early games focused on World War II, where the series established itself. It became a gaming phenomenon when it moved to “Modern Warfare” and starred characters such Capt. John Price and Soap MacTavish.

“Call of Duty” has has other iterations in between but arguably the most beloved line is “Black Ops.” It’s the subseries, in which Treyarch established itself as the lead developer of a franchise that Infinity Ward started. It also set the standard for the robust multiplayer experience that fans have come to expect.