London Protocol
The German population in Schleswig and Holstein revolted, inspired by the Protestant clergy. The German states sent in an army, but Danish victories in 1849 led to the Treaty of Berlin (1850) and the London Protocol (1852). They reaffirmed the sovereignty of the King of Denmark, while prohibiting union with Denmark. The violation of the latter provision led to renewed warfare in 1863 and the Prussian victory in 1864.