Battle of Jena–Auerstedt
After the defeat of the Prussian Army by the French at the Battle of Jena–Auerstedt, the Treaty of Tilsit in 1807 made the easternmost portion of today's Westphalia part of the French client Kingdom of Westphalia until 1813, when the kingdom was dissolved by the Russians. While this state shared its name with the historical region, it only contained a relatively small part of Westphalia, rather consisting of mostly Hessian and Eastphalian regions.