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Duchy of Schleswig

Early history

Roman sources place the homeland of the tribe of Jutes north of the river Eider and that of the Angles south of it. The Angles in turn bordered the neighbouring Saxons. By the early Middle Ages, the region was inhabited by three groups:
* Danes (including assimilated Jutes), who lived north of the Danevirke and the Eckernförde Bay,
* North Frisians, who lived in most of North Frisia, including on the North Frisian Islands, and
* Saxons (including Germanized Wagrians and Wends), who lived in the area south of the Danes and the Frisians.

During the 14th century, the population on Schleswig began to speak Low German alongside Danish, but otherwise the ethno-linguistic borders remained remarkably stable until around 1800, with the exception of the population in the towns that became increasingly German from the 14th century onwards.

During the early Viking Age, Haithabu – Scandinavia’s biggest trading centre – was located in this region, which is also the location of the interlocking fortifications known as the Danewerk or Danevirke. Its construction, and in particular its great expansion around 737, has been interpreted as an indication of the emergence of a unified Danish state. Towards the end of the Early Middle Ages, Schleswig formed part of the historical Lands of Denmark as Denmark unified out of a number of petty chiefdoms in the 8th to 10th centuries in the wake of Viking expansion.


The southern boundary of Denmark in the region of the Eider River and the Danevirke was a source of continuous dispute. The Treaty of Heiligen was signed in 811 between the Danish King Hemming and Charlemagne, by which the border was established at the Eider. During the 10th century, there were several wars between East Francia and Denmark. In 1027, Conrad II of Germany and Canute the Great again fixed their mutual border at the Eider.

In 1115, King Niels created his nephew Canute Lavard – a son of his predecessor Eric I – Earl of Schleswig, a title used for only a short time before the recipient began to style himself Duke.

Valdemar II was the second son of King Valdemar I of Denmark and Sophia of Minsk, the daughter of Richeza of Poland, Queen Dowager of Sweden and Volodar Giebovich, Prince of Minsk. When his father died, young Valdemar was only twelve years old. He was named Duke of Southern Jutland (Latin: dux slesvicensis, literally Duchy of Schleswig).

Young Duke Valdemar of Schleswig (prior to becoming King of Denmark) faced a threat from Adolph III, Count of Schauenburg and Holstein. The Count tried to stir up other German Counts to take southern Jutland from Denmark, and to assist Bishop Valdemar’s plot to take the Danish throne. With the Bishop again in prison, Duke Valdemar went after Count Adolph, and with his own troop levies, he marched south and captured Adolph’s new fortress at Rendsburg. He defeated and captured Count Adolph III at the Battle of Stellau in 1201, and imprisoned him in a cell next to Bishop Valdemar. Two years later, due to an illness, Count Adolph III was able to buy his way out of prison by ceding all of Schleswig, north of the Elbe, to Duke Valdemar. In November 1202, Duke Valdemar’s elder brother, King Canute VI, died unexpectedly at the age of 40, leaving no heirs.

In the 1230s, Southern Jutland (the Duchy of Schleswig) was allotted as an appanage to Abel Valdemarsen (1218 – June 29, 1252) was Duke of Schleswig from 1232 to 1252 and King of Denmark from 1250 until his death in 1252. He was the son of Valdemar II by his second wife, Berengaria of Portugal, and brother to Eric IV and Christopher I, and Canute’s great-grandson.

Abel, having wrested the Danish throne for himself for a brief period, left the Duchy of Schleswig to his sons and their successors, who pressed claims to the throne of Denmark for much of the next century, so that the Danish kings were at odds with their cousins, the Duke of Schleswig.

Feuds and marital alliances brought the Abel dynasty into a close connection with the German Duchy of Holstein by the 15th century. The latter was a fief subordinate to the Holy Roman Empire, while Schleswig remained a Danish fief. These dual loyalties were to become a main root of the dispute between the German states and Denmark in the 19th century, when the ideas of romantic nationalism and the nation-state gained popular support.

Early modern times

The title of Duke of Schleswig was inherited in 1460 by the hereditary kings of Norway, who were also regularly elected kings of Denmark simultaneously, and their sons (unlike Denmark, which was not hereditary). This was an anomaly– a king holding a ducal title of which he as king was the fount and liege lord. The title and anomaly survived presumably because it was already co-regally held by the king’s sons. Between 1544 and 1713/20, the ducal reign had become a condominium, with the royal House of Oldenburg and its cadet branch House of Holstein-Gottorp jointly holding the stake. A third branch in the condominium, the short-lived House of Haderslev, was already extinct in 1580 by the time of John the Elder.

Following the Protestant Reformation, when Latin was replaced as the medium of church service by the vernacular languages, the diocese of Schleswig was divided and an autonomous archdeaconry of Haderslev created. On the west coast, the Danish diocese of Ribe ended about 5 km (3 miles) north of the present border. This created a new cultural dividing line in the duchy because German was used for church services and teaching in the diocese of Schleswig and Danish was used in the diocese of Ribe and the archdeaconry of Haderslev. This line corresponds remarkably closely with the present border.

In the 17th century a series of wars between Denmark and Sweden—which Denmark lost—devastated the region economically. However, the nobility responded with a new agricultural system that restored prosperity. In the period 1600 to 1800 the region experienced the growth of manorialism of the sort common in the rye-growing regions of eastern Germany. The manors were large holdings with the work done by feudal peasant farmers. They specialized in high quality dairy products. Feudal lordship was combined with technical modernization, and the distinction between unfree labour and paid work was often vague. The feudal system was gradually abolished in the late 18th century, starting with the crown lands in 1765 and later the estates of the nobility. In 1805 all serfdom was abolished and land tenure reforms allowed former peasants to own their own farms.

19th century and the rise of nationalism

From around 1800 to 1840, the Danish-speaking population on the Angeln peninsula between Schleswig and Flensburg began to switch to Low German and in the same period many North Frisians also switched to Low German. This linguistic change created a new de facto dividing line between German and Danish speakers north of Tønder and south of Flensburg. From around 1830, large segments of the population began to identify with either German or Danish nationality and mobilized politically. In Denmark, the National Liberal Party used the Schleswig Question as part of their agitation and demanded that the Duchy be incorporated into the Danish kingdom under the slogan “Denmark to the Eider”.

This caused a conflict between Denmark and the German states over Schleswig and Holstein, which led to the Schleswig-Holstein Question of the 19th century. When the National Liberals came to power in Denmark in 1848, it provoked an uprising of ethnic Germans who supported Schleswig’s ties with Holstein. This led to the First War of Schleswig. Denmark was victorious and the Prussian troops were ordered to pull out of Schleswig and Holstein following the London Protocol of 1852.