Charles Augustus, 1757–1828, duke and, after 1815, grand duke of Saxe-Weimar-Eisenach; friend and patron of Goethe, Schiller, and Herder. Though his duchy was small, he was important in German politics. He helped Frederick II of Prussia form (1785) the Fürstenbund [league of princes] to check Austria's attempt under Holy Roman Emperor Joseph II to expand Austrian influence in the empire. He fought in the French Revolutionary Wars and against Napoleon I until 1806, when he was forced to join the Confederation of the Rhine. At the Congress of Vienna after Napoleon's defeat his duchy was enlarged and he was raised to a grand duke. Assisted by Goethe, he made Weimar a center of literature, science, art, and liberal political thought. In 1816 he introduced a constitution.