https://www.gamespot.com/articles/call-of-duty-black-ops-4-release-date-blackout-zom/1100-6462428/

Call of Duty: Black Ops 4 continues the franchise's history of explosive multiplayer, first-person shooter combat. Old mechanics and features return, such as the fan favorite Zombie mode, but the game implements several changes to the Black Ops formula. We've compiled everything we know about Black Ops 4 so far, and will continue to update this post as we discover more about the game.

Black Ops has a pretty lengthy history. The first, releasing in 2010, takes place during the Cold War in the 1960s, switching between CIA operatives Alex Mason and Frank Woods. 2012's Black Ops 2 moved the story to 2025, following Alex's son, David Mason. 2015's Black Ops 3, continued the previous game's journey into the future and followed operatives in 2065.