Kammala wannan jumla: A cikin 1804 Duke Charles Augustus ya shiga siyasar Turai ta hanyar auren dansa kuma magaji Charles Frederick zuwa Grand Duchess Maria Pavlovna, 'yar'uwar Sarkin sarakuna Alexander I na Rasha. Duk da haka, a lokaci guda ya shiga Prussia a cikin
Yaƙin Hadin Gwiwa na Hudu a kan Daular Faransa, kuma bayan shan kashi a Yaƙin Jena-Auerstedt an tilasta shi shiga cikin Napoleon Confederation na Rhine a 1806. A cikin 1809 Saxe-Weimar da Saxe-Eisenach, waɗanda aka haɗa su ne kawai a cikin mutumin Duke, an haɗa su a cikin Duchy na Saxe-Weimar-Eisenach.