They Shall Not Pass delivers some new vehicles to the game.
One new vehicle is a super-heavy tank from France called the Char 2C.
The Char 2C was developed during the war. And while it eventually rolled off the assembly line, the Char 2C was deployed after World War I ended. You can get a feel for it in the footage below.
This tank joins the likes of the Dreadnaught, zeppelin, and armored train as a behemoth class vehicle.
The other vehicle is the Assault Tank Gun, also known as the St. Chamond. The Assault Tank Gun "was most heavily armed allied tank of the war" and like the Char 2C, its of French origin.
The St. Chamond in Battlefield 1 features a 75mm Cannon and five Hotchkiss M1914 machine guns. You can also choose from three packages including a Field Assault Package, Gas Assault Package, Standoff Assault Package.
DICE is reportedly thinking about bringing the DLC vehicles to the vanilla version of the game though this would likely be done through a custom game mode.