Upon the death of Charles Joseph, Elector of Trier, in 1715, under the terms of the Treaty of Westphalia, it was the turn of a Protestant to become Prince-Bishop of Osnabrück. This position as a Prince of the Holy Roman Empire and ruler of an independent principality had to alternate between Catholics and Lutherans according to the treaty. Usually a member of the House of Welf held the office whenever the turn came to Protestants.