In 1805 he became Professor of Medicine in Kiel (then in Denmark and part of the Duchy of Holstein) with the title Counsellor of Justice and, later Counsellor of State. These were difficult years for Denmark which had sided with France in the Napoleonic Wars against England (and her allies) to preserve her maritime empire. Money was a problem and Wiedemann used his own resources to set up the midwifery clinic proposed as one of his duties as professor.