https://wccftech.com/call-of-duty-modern-warfare-beta-ground-war/

Call of Duty: Modern Warfare wrapped up the PS4-exclusive first leg of its open beta this past weekend, and PC and Xbox One owners will get to join the fun (and play together with PS4 owners via crossplay) this coming weekend. The first half of the open beta focused on traditional 6v6 Call of Duty multiplayer and the new 2v2 Gunfight mode, but Activision has announced the new 32v32 Ground War mode will also be playable during the second half of the beta. This was surprise-revealed via the following in-game message:

Thank you for playing the Call of Duty: Modern Warfare Beta! We hope you’re enjoying everything we’ve shown you so far, but we aren’t done yet! On Saturday, September 21, during weekend two of the Beta, we’ll be taking your multiplayer experience to the next level. Taking place on a new map, Karst River Quarry, you’ll get your hands on 32v32 warfare in a new mode, Ground War.