The Danish language decrees of 1851 were a language policy measure introduced by the conservative Danish government of the time with the aim of halting the language shift to German in the central parts of the Duchy of Schleswig and binding Schleswig more closely to the Kingdom of Denmark through closer alignment of its language and culture after the suppression of the Schleswig-Holstein uprising of 1848/1849. To this end, Danish was introduced as the language of instruction in 58 municipalities in the central Schleswig area, where Danish was still widely spoken but German was often already the predominant language. Church services were to be conducted alternately in German and Danish. Court proceedings were to use the language preferred by the persons concerned.

Schleswig itself was multilingual, with Danish predominating in the north, German in the south, and Frisian in parts of North Frisia. In the central areas (such as Angeln and the Geest), a language shift from Danish to German took place in the 19th century. The language issue had already been an important aspect of the Schleswig-Holstein question in the first half of the 19th century. With growing nationalism, the mother tongue became increasingly important as a sign of national identity. The language decrees can thus be understood as an expression of Denmark's desire for a nation state with a uniform language and culture. On the part of the German-minded Schleswig-Holsteiners, however, the attempt at forced Danishization led to increased hatred of the Danes and contributed to the breakup of the Danish Unitary State. After Denmark's defeat in the German-Danish War of 1864, the Danish language decrees were repealed. In the Prussian province of Schleswig-Holstein, the Danish language was then suppressed in North Schleswig from 1871 onwards with similar measures.

Background The Duchy of Schleswig had been a Danish fiefdom since the Middle Ages. The Treaty of Ribe in 1460 established a personal union with the Kingdom of Denmark. The Danish Unitary State was a multinational state held together by loyalty to a common ruler. Within the state, German had been the dominant language of the upper classes and the educated since the 15th century. In the 18th century, Germans formed a significant part of the upper class and cultural life of the capital Copenhagen. Even the kings from the House of Oldenburg, their wives, most of whom came from German ruling houses, and the members of the government, who for centuries were recruited from German noble families, often did not speak Danish. It was not until Christian VII that criticism of the dominance of German became vocal, mainly in response to the government of the German Johann Friedrich Struensee. After 1772, Ove Høegh-Guldberg introduced Danish as the command language of the army. At the same time, a distinct Danish literature developed.

Multilingualism in Schleswig Schleswig had been a "language contact area" since the Middle AgesMogens Dyhr: Der deutsch-dänische Sprachkonflikt in Schleswig im 19. Jahrhundert, in: Dieter Cherubim und andere (Hrsg.): Sprache und bürgerliche Nation, Berlin/New York 1998, pp. 101–121; p. 101. and remained multilingual throughout the 19th century. The rural population, which made up around 90% of the inhabitants,Ole Feldbæk: Dänisch und Deutsch im dänischen Gesamtstaat im Zeitalter der Aufklärung, in: Bohnen, Klaus / Jørgensen, Sven-Aage (Hrsg.): Der dänische Gesamtstaat. Kopenhagen – Kiel – Altona. Wolfenbüttler Studien zur Aufklärung Band 18. Tübingen 1992, p. 7–22. used various languages and dialects in everyday life. Many Schleswigers were multilingual. About half of them used Danish dialects at least some of the time, especially the various dialects of Sønderjysk (South Jutlandic). During the first half of the 19th century, the area in which Danish dialects were predominant in everyday life shifted northward. Angel Danish, spoken in Angeln and Schwansen,„Die Landschaft auf der südlichen Seite der Schley heißt Schwansen [...] Die Einwohner sind hier ebenfalls ächte Dänen, wenn auch ihre Mundart von einem Kopenhagener oder Norweger nicht leicht verstanden wird. [...] Jetzt hört die Dänische Sprache auch beym Landvolke auf und die Plattdeutsche tritt ausschließlich an deren Stelle.“ Aus: with its increasing use of German loanwords, was more of a mixed language than a Danish dialect and had been disappearing since the end of the 18th century. South of the Schleswig–Husum line, Low German was spoken almost exclusively. At the time of the language change, another language island finally formed in the mid-19th century in the parish of Viöl, located on the Geest, with the South Jutlandic dialect Fjoldemål. On the west coast between Husum and the Vidå, the North Frisian dialects, which varied from place to place, were widespread. None of these languages had a written form or even literature. The Danish and Frisian dialects were mostly spoken as regional languages in a locally limited area, so that mastery of at least one other language was necessary for supraregional communication. Since the people of South Schleswig were mostly economically oriented towards the south, knowledge of German was indispensable.Jochen Bracker: Die dänische Sprachpolitik 1850–1864 und die Bevölkerung Mittelschleswigs. In: Zeitschrift für Schleswig-Holsteinische Geschichte 97 (1972), pp. 127–226; p. 138.

Together with the purely German-speaking Duchy of Holstein, Schleswig was administered by the German Chancellery, whose administrative language was High German. By 1700, High German had already replaced Low German as the sole official language. However, only the relatively small urban upper class spoke High German. Nevertheless, High German was also the language of the church and schools in the communities south of what later became the Clausen Line and in all cities. In the rural communities north of this line, sermons were preached at least partly in standard Danish – and hymns from the German hymnbook were sung in the same service, as there was no Danish hymnbook for Schleswig for a long time.Carl Ferdinand Allen: Geschichte der dänischen Sprache im Herzogthum Schleswig oder Südjutland. Schleswig 1858. 2. Teil, p. 5. The Christelig Psalmebog of 1801 was rejected by many Pietist Danish-speaking communities because of its rationalist character. In rural schools in North Schleswig, lessons were often taught in Danish, although Danish-language textbooks were not introduced until the end of the 18th century. The unwritten vernacular languages and dialects were deliberately combated by secular and ecclesiastical authorities. On the one hand, this was done to create uniformity. On the other hand, there was a prevailing assumption that education was only possible in the standard language. For example, the catechism necessary for understanding Lutheran doctrine was only available in the standard language, which is why most preachers attached great importance to teaching High German in schools. The view that High German was the language of education was also widespread among the population. As a result, the number of parents who spoke German with their children instead of Danish or Frisian increased steadily. Within a few decades, the native language changed. The use of everyday Danish became increasingly a phenomenon of the lower classes. But especially in circles where High German was not widely spoken, the High German language of the church was given a sacred meaning similar to that of Latin in the Catholic Church.Jochen Bracker: Die dänische Sprachpolitik 1850–1864 und die Bevölkerung Mittelschleswigs. In: Zeitschrift für Schleswig-Holsteinische Geschichte 97 (1972), pp. 127–226; p. 136. Only a few pastors spoke out in favor of aligning the language of the church and schools with the vernacular to ensure that their congregations truly understood the Christian message.Lars N. Henningsen: Unter Dänemark. In: Ders.: Zwischen Grenzkonflikt und Grenzfrieden. Die dänische Minderheit in Schleswig-Holstein in Geschichte und Gegenwart. Studieafdelingen ved Dansk Centralbibliotek for Sydslesvig Nr. 65. Flensburg 2011, pp. 11–48; p. 23.

Language as a political issue in the first half of the 19th century Until the crises triggered by the Napoleonic Wars at the beginning of the 19th century, the Danish state as a whole was considered a progressive state in which the nationality and language of its inhabitants were not accorded any significance beyond everyday life. The Danish king was revered equally by all his subjects, regardless of their mother tongue.

The language laws of 1806 and 1810 In 1806, the Holy Roman Empire, to which the Duchy of Holstein belonged, was dissolved. The Danish king Christian VII then declared the Duchy of Holstein, which had belonged to the Empire, to be an "inseparable part" of the Danish Kingdom. In 1807, a law required all officials of the duchies to be proficient in both (standard) languages. All public decrees in both duchies were to be published in both languages with immediate effect. On December 15, 1810, Frederick VI then issued a law stipulating that Danish should be the language of administration, courts, schools, and churches wherever the population spoke Danish in everyday life.Michael Bregnsbo: Die Einverleibung Holsteins im Jahre 1806 und die Reaktion Dänemarks auf die Auflösung des alten Reichs. In: Michael North / Robert Riemer (pub.): Das Ende des Alten Reiches im Ostseeraum: Wahrnehmungen und Transformationen. Köln / Weimar 2008, p. 116–125. The German civil servants of the German Chancellery and in the local offices opposed the introduction, arguing that, firstly, they themselves did not speak Danish and, secondly, the “crow's Danish” spoken in Central Schleswig was about as far removed from Imperial Danish as it was from High German. Nevertheless, a chair for the Danish language was established at Kiel University, and all future officials in the duchies were required to master the Danish language.Lars N. Henningsen: Unter Dänemark. In: Ders.: Zwischen Grenzkonflikt und Grenzfrieden. Die dänische Minderheit in Schleswig-Holstein in Geschichte und Gegenwart. Studieafdelingen ved Dansk Centralbibliotek for Sydslesvig Nr. 65. Flensburg 2011, pp. 11–48; pp. 25.

The school reform introduced by Generalsuperintendent Jacob Georg Christian Adler in 1814 standardized teaching content, raised educational standards, and enforced compulsory education more strictly than before. However, Danish was only intended as the language of instruction in rural schools in areas where Danish was the language of the church, but not in urban schools and in mixed-language areas. Although it took several decades for the reform to take hold, it ultimately led to a strengthening of German in North Schleswig as well. In Central Schleswig, the increasing literacy in High German accelerated the extinction of the Danish dialects, as the population realized that mastery of (High) German provided educational and thus social advancement opportunities, and parents therefore tended to speak German rather than Angle-Danish with their children.

With the Congress of Vienna in 1815, Holstein became part of the German Confederation. Denmark was required to treat both duchies equally and not to strengthen its hold on Schleswig. The language laws of 1807 and 1810 remained largely unheeded.