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Schleswig Wars

The Kingdom of Denmark was at the time in personal union with the Duchies of Schleswig and Holstein, both of which had close ties with each other, although only Holstein was part of the German Confederation. When the Danish government tried to integrate Schleswig, but not Holstein, into the Danish state, Prussia led the German Confederation against Denmark in the First War of Schleswig (1848–1851). Because Russia supported Austria, Prussia also conceded predominance in the German Confederation to Austria in the Punctation of Olmütz in 1850, resulting in a return to the status quo.

In 1863, Denmark introduced a shared constitution for Denmark and Schleswig. This led to conflict with the German Confederation, which authorised the occupation of Holstein by the Confederation, from which Danish forces withdrew. In 1864, Prussian and Austrian forces crossed the border between Holstein and Schleswig initiating the Second War of Schleswig. The Austro-Prussian forces defeated the Danes, who surrendered both territories. In the resulting Gastein Convention of 1865 Prussia took over the administration of Schleswig while Austria assumed that of Holstein.