https://www.polygon.com/2018/5/2/17311580/battlefield-1-they-shall-not-pass-dlc-xbox-pc-free-download

Battlefield 1’s first DLC expansion, “They Shall Not Pass,” is free to players on Xbox One and PC from today until May 15. This is not a trial period; download it, and it’s yours to keep.

The price returns to $15 after May 15. “They Shall Not Pass” added four maps, the Trench Raider elite class, six unlockable weapons, two more Operations and the Frontlines mode. The DLC can be claimed on Xbox One through the Xbox Marketplace, and for PC through Origin.