Call of Duty WWII's first community event is called Winter Siege and it will run starting December 8 to January 2, 2018 on PS4, Xbox One, and PC.
There's a lot coming to the multiplayer portion of the game during this time. For one, players will be getting a winter version of the Carentan multiplayer map, which is pretty much a snow-covered version of the exclusive map given to those that opt for the season pass. New weapons will be added into the game for free, as well as a non-stop schedule of playlists with double XP. During the second week, a fan favorite game mode called Gun Game will make a return for a limited time.
Headquarters, the game's social hub, will receive a winter-y update to fit with the ongoing event. A new Quartermaster will also be around for Winter Siege - Captain Bitcher will be around HQ bearing unique Winter Siege Division uniforms, cosmetic items, and unique weapon variants. These special variants can be earned through special orders given by Major Howard, which is the NPC that provides the daily and weekly orders (challenges)
Lastly, players will be given a special loot crate for the Winter Siege event each week containing event-specific cosmetic rewards. A few fixes to the game are also coming together with community event when it goes live. You can have a look at the patch notes here.