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 early 1848, it provoked an uprising of ethnic Germans in the duchies. This led to the First War of Schleswig (1848–51). The Schleswig-Holsteiners were supported by the German Confederation of which Holstein (and Lauenburg) was a member state. Although Schleswig was never a part of the Confederation, the Confederation (and the short-lived German Empire of that time) treated Schleswig largely as such. The ideological argument was not only an ethnic but also a historical one: the German side referred to a medieval treaty that claimed that Schleswig and Holstein should be forever united (in Low German: up ewig ungedeelt). The federal and then imperial troops consisted mainly of Prussian divisions. Under pressure of the other great powers, Prussia had to retreat (in summer 1848 and again in summer 1850). This left the Schleswig-Holstein rebels to their fate. In 1851 the rebel government and its army were disbanded. In the London Protocol of 1852 the great powers confirmed that the king of Denmark was the duke of the duchies but also the status of the duchies as being distinct from Denmark proper. Denmark again attempted to integrate Schleswig by creating a new common constitution (the so-called November Constitution) for Denmark and Schleswig in 1863. This was met by German states in two ways: The German Confederation send troops to Holstein (and Lauenburg) which was a member state. This internal Bundesexekution was meant to force the duke (= the king of Denmark) to respect the status of the duchy. The troops occupying Holstein were mainly from Hanover and Saxony, with Austrian and Prussian troops waiting as a reserve. Austria and Prussia, against the will of the Confederation, in February 1864 let their troops cross the border between Holstein and Schleswig. Occupying Schleswig also was supposed to