 In 1521, it was passed on to Duke Ulrich von Württemberg, who developed Hohentwiel into one of the strongest fortresses of his duchy.During this time, it began to be used as a prison, and in 1526, Hans Müller von Bulgenbach, a peasant commander, was imprisoned there before he was executed.The fortress resisted five Imperial sieges in the Thirty Years' War, under the command of Konrad Widerholt between 1634 and 1648.