As revealed about a week and half ago, the first major expansion to Battlefield 1 is now live, but only to Premium Pass holders. The DLC, They Shall Not Pass, includes 4 new maps; 2 new tanks; a new character class - the Trench Raider Elite; the Siege Howitzer stationary gun; 2 new operations; new weapons, medals, dog tags, and other unlockables; and the ability to take to the battlefield as the French army.
The Premium Pass is simply the DLC season pass bundle that will include all 4 planned Battlefield 1 DLCs. It's $50 and offers a two week headstart on each of the DLCs. So for the rest of us that means They Shall Not Pass will be going live at the end of the month.
To learn more about the They Shall Not Pass DLC go to the official website, where you can also find more information about the Premium Pass.