The Duchy of Saxe-Weimar-Eisenach was created in 1809 when the Ernestine duchies of Saxe-Weimar and Saxe-Eisenach were formally joined into one state . The Duchy of Saxe-Weimar-Eisenach was created in 1809 by the merger of the Ernestine duchies of Saxe-Weimar and Saxe-Eisenach .