https://www.gamespot.com/articles/free-battlefield-1-dlc-available-now-on-ps4xbox-on/1100-6459112/

Presumably to celebrate the upcoming reveal of Battlefield V, EA giving away one of the expansion packs for 2016's Battlefield 1. The game's In the Name of the Tsar expansion, which includes a new army and six more maps, is now free on Xbox One and PS4.

You can download it from your console or queue up your download from the PlayStation and Xbox stores by following the links. The freebie does not appear to be available on PC (at least not yet).