In preparation for the peace conference that was expected to follow World War I, in the spring of 1917 the British Foreign Office established a special section responsible for preparing background information for use by British delegates to the conference. Schleswig-Holstein is Number 35 in a series of more than 160 studies produced by the section, most of which were published after the conclusion of the 1919 Paris Peace Conference. The duchies of Schleswig and Holstein were ruled by the king of Denmark until 1864 when, as a consequence of a short war by Austria and Prussia against Denmark, they were brought under joint Austro-Prussian rule. The condominium of the two great German powers existed only until 1866, when, as a consequence of the Austro-Prussian War of that year, both duchies came under exclusive Prussian control and were merged to form the Prussian province of Schleswig-Holstein. The inhabitants of Holstein were overwhelmingly German speaking, those of Schleswig mainly Danish speaking, although for centuries German had been spreading to more and more territory north of the Eider River (the boundary between the two duchies and traditionally the frontier between Germany and Scandinavia). A small Frisian-speaking minority also inhabited parts of mainland Schleswig and several islands of the duchy. The book covers physical and political geography, political history, social and political conditions, and economic conditions, with by far the largest part taken up by the historical section and its discussion of the political, diplomatic, military, dynastic, and linguistic aspects of the disputes over control of the province. The population of Schleswig-Holstein is given as 1,621,004 in 1910. The economic section stresses the importance of the Kiel Canal linking the Baltic and North Seas (built by Germany and opened in 1895), the industrial ports of Kiel and Altona, and the wealth generated by the province’s small farms and haddock, herring, and cod fisheries. Following Germany’s defeat in World War I, the Treaty of Versailles stipulated that the future of Schleswig was to be determined by a plebiscite. The vote was held in February 1920. Three-quarters of the population elected in favor of union with Denmark, and in July 1920 the province was incorporated into Denmark. Holstein remained a part of Germany.

Last updated: February 4, 2016