Call of Duty: Modern Warfare II is adding raids after launch, and now Infinity Ward has shed some additional light on what to expect from them.

Little is known about the raids in Modern Warfare II, but Infinity Ward said fans can expect each raid to “advance [the] ongoing story, as old friends and new enemies tie up loose ends…”

As announced previously, raids are coming to Modern Warfare II on December 14 with the start of Season 1 Reloaded. Raids will seemingly exist within Spec Ops. A blog post from earlier in October states that on December 14, “Special Ops receives the very first episode of raids for Operators to master.”

Raids in Modern Warfare II are described as a “whole new experience” for Call of Duty. They take the form of a three-player co-op “engagement” that Activision says will require “teamwork and strategic puzzle-solving” in between intense firefights.

Raids are known to be exciting and challenging in other games that have them, like Bungie’s Destiny 2. As mentioned, the Call of Duty series has never had raids, so it’ll be interesting to see how they are implemented.

While fans have to wait until December for raids, Modern Warfare II’s full release–covering campaign and multiplayer–is set for October 28. For more, check out GameSpot’s Call of Duty: Modern Warfare II campaign review and read up on everything you need to know about pre-loading and launch times.