When the Danish government tried to integrate Schleswig, but not Holstein, into the Danish state, Prussia led the German Confederation against Denmark in the First War of Schleswig (1848–1851).
Ketika pemerintah Denmark mencoba untuk mengintegrasikan Schleswig tapi tidak Holstein kedalam negara Denmark, Prusia memimpin Konfederasi Jerman melawan Denmark dalam Perang Schleswig Pertama (1848-851).