What was the Eider Program in Danish politics?

The Eider Program (1848–1864) was the cornerstone of domestic and foreign policy for Denmark’s National Liberal governments during the Schleswig-Holstein crises.1

Driven by the "Eider-Dane" nationalist movement, the program sought to establish the Eider River—the historical boundary between the duchies of Schleswig and Holstein—as the permanent national frontier of Denmark. The primary goal was to formally incorporate the duchy of Schleswig into the Danish state while detaching it from its long-standing association with Holstein.123

This policy directly conflicted with the aspirations of German nationalists, who sought to keep the two duchies united and linked to the German Confederation. The program faced significant international opposition, as it violated agreements intended to maintain the constitutional separation of Schleswig from Denmark. Efforts to implement the program, particularly through the constitution of 1863, ultimately provoked the German-Danish War of 1864, resulting in Denmark's defeat and the loss of both duchies to Prussia and Austria.3214