The Schleswig War, also known as the First Schleswig War, occurred from 1848 to 1851 between the Kingdom of Denmark and the German Confederation. The conflict arose over the duchies of Schleswig and Holstein, which were predominantly German-speaking regions but ruled by the Danish king. Tensions escalated when nationalist movements sought to unite these duchies with Germany. The war ended with the Treaty of Berlin in 1851, which restored Danish control over Schleswig and Holstein. However, the conflict highlighted the growing tensions between Denmark and the German states, setting the stage for future disputes, including the Second Schleswig War in 1864.