I te tau 1804 ka uru a Duke Charles Augustus ki nga mahi torangapu o Europi ma te marenatanga o tana tama me te rangatira o Charles Frederick ki te Grand Duchess Maria Pavlovna, te tuahine o Emperor Alexander I o Russia. Heoi anō, i taua wā anō, ka uru atu ia ki a Puruhi i te Pakanga o te Wā o te Wā o te Wā
I muri i te hinganga i te Pakanga o Jena-Auerstedt i akiakihia kia uru atu ki te Napoleon Confederation o te Rhine i te tau 1806. I te tau 1809 Saxe-Weimar me Saxe-Eisenach, i whakakotahihia anake i roto i te tangata o te rangatira, i whakakotahihia ki te Duchy o Saxe-Weimar-Eisenach.