 In 1813, after the expulsion of Bonaparte and the reinstatement of an elector, Grimm was appointed Secretary of Legation accompanying the Hessian minister to the headquarters of the allied army.In 1814, he was sent to Paris to demand restitution of books taken by the French, and he attended the Congress of Vienna as Secretary of Legation in 1814–1815.Upon his return from Vienna, he was sent to Paris again to secure book restitutions.