Saxe-Lauenburg in the context of "Schleswig"

Jutland (/ˈdʒʌtlənd/), historically known as the Cimbrian Peninsula, is a peninsula in Northern Europe that forms the continental portion of Denmark and part of northern Germany (Schleswig-Holstein). It stretches from the Grenen spit in the north to the confluence of the Elbe and the Sude in the southeast. The historic southern border river of Jutland as a cultural-geographical region, which historically also included Southern Schleswig, is the Eider. The peninsula, on the other hand, also comprises areas south of the Eider: Holstein, the former duchy of Lauenburg, and most of Hamburg and Lübeck.

Jutland's geography is flat, with comparatively steep hills in the east and a barely noticeable ridge running through the center. West Jutland is characterised by open lands, heaths, plains, and peat bogs, while East Jutland is more fertile with lakes and lush forests. The southwestern coast is characterised by the Wadden Sea, a large, unique international coastal region stretching through Denmark, Germany, and the Netherlands. The peninsula's longest river is the Eider, which rises close to the Baltic but flows in the direction of the North Sea due to a moraine, while the Gudenå is the longest river of Denmark. In order for ships not having to go around the whole peninsula to reach the Baltic, the Kiel Canal – the world's busiest artificial waterway, crossing the peninsula in the south – was constructed.

The Duchy of Schleswig (/ˈʃlɛswɪɡ/; German: [ˈʃleːsvɪç]; Danish: Hertugdømmet Slesvig; German: Herzogtum Schleswig; Low German: Hartogdom Sleswig; North Frisian: Härtochduum Slaswik) was a duchy in Southern Jutland (Sønderjylland) covering the area between about 60 km (35 miles) north and 70 km (45 mi) south of the current border between Germany and Denmark. The territory has been divided between the two countries since 1920, with Northern Schleswig in Denmark and Southern Schleswig in Germany. The region is also called Sleswick in English.

Unlike Holstein and Lauenburg, Schleswig was never a part of the German Confederation. Schleswig was instead a fief of Denmark, and its inhabitants spoke Danish, German, and North Frisian. Both Danish and German National Liberals wanted Schleswig to be part of a Danish or German national state in the 19th century. A German uprising in March 1848 caused the First Schleswig War which ended in 1852. The Second Schleswig War (1864) ended with the three duchies being governed jointly by Austria and Prussia. In 1866, they became a part of Prussia.

The First Schleswig War (German: Schleswig-Holsteinischer Krieg), also known as the Schleswig-Holstein uprising (German: Schleswig-Holsteinische Erhebung) and the Three Years' War (Danish: Treårskrigen), was a military conflict in southern Denmark and northern Germany rooted in the Schleswig–Holstein question: who should control the Duchies of Schleswig, Holstein and Lauenburg, which at the time were ruled by the king of Denmark in a personal union. Ultimately, the Danish side proved victorious with the diplomatic support of the great powers, especially Britain and Russia, since the duchies were close to an important Baltic seaway connecting both powers.

While Schleswig had been predominantly Danish with a German elite concentrated in the cities and estates, modernisation brought extensive German influence. German became the language of administration, education, and the church, creating an environment in which it was omnipresent and speaking Danish offered no advantages. Due to top-down pressure, many Danish South Schleswigers gradually adopted German in their daily lives. This linguistic shift led to the extinction of the two Danish South Schleswig dialects, Fjoldemål and Angeldanish – first in favour of Low German, and later High German. Over time, these now Low German-speaking South Schleswigers became fully Germanized, came to identify with the German question, and sought to separate Schleswig, along with Holstein, from Denmark entirely. Therefore, by the outbreak of the war, Schleswig was divided: a Danish-speaking North and a Low German-speaking South, while Holstein and Lauenburg were entirely ethnically German.

Christian IX (8 April 1818 – 29 January 1906) was King of Denmark from 15 November 1863 until his death in 1906. From 1863 to 1864, he was concurrently Duke of Schleswig, Holstein and Lauenburg.

A younger son of Frederick William, Duke of Schleswig-Holstein-Sonderburg-Glücksburg, Christian grew up in the Duchy of Schleswig as a prince of Schleswig-Holstein-Sonderburg-Glücksburg, a junior branch of the House of Oldenburg which had ruled Denmark since 1448. Although having close family ties to the Danish royal family, he was originally not in the immediate line of succession to the Danish throne. Following the early death of his father in 1831, Christian grew up in Denmark and was educated at the Military Academy of Copenhagen. After unsuccessfully seeking the hand of Queen Victoria of the United Kingdom in marriage, he married his double second cousin, Princess Louise of Hesse-Kassel, in 1842.

Duchy of Lauenburg (German: Herzogtum Lauenburg [ˈhɛʁtsoːktuːm ˈlaʊənbʊʁk] ) is the southernmost Kreis, or district, officially called District of Duchy of Lauenburg (German: Kreis Herzogtum Lauenburg), of Schleswig-Holstein, Germany. It is bordered by (from the west and clockwise) the district of Stormarn, the city of Lübeck, the state of Mecklenburg-Vorpommern (districts of Nordwestmecklenburg and Ludwigslust-Parchim), the state of Lower Saxony (districts of Lüneburg and Harburg), and the city state of Hamburg. The district of Herzogtum Lauenburg is named after the former Duchy of Saxe-Lauenburg.