Second Schleswig War

The Second Schleswig War or German-Danish War, also sometimes known as the Dano-Prussian War or Prusso-Danish War, was the second military conflict over the Schleswig–Holstein question of the 19th century. The war began on 1 February 1864, when Prussian and Austrian forces crossed the border into the Danish fief Schleswig. Denmark fought troops of the Kingdom of Prussia and the Austrian Empire representing the German Confederation. Like the First Schleswig War (1848–1852), it was fought for control of the duchies of Schleswig, Holstein, and Lauenburg. Succession disputes concerning the duchies arose when Frederick VII, King of Denmark died without an heir acceptable to the German Confederation. The war started after the passing of the November Constitution of 1863, which tied the Duchy of Schleswig more closely to the Danish kingdom, which was viewed by the German side as a violation of the London Protocol. The war ended on 30 October 1864, with the Treaty of Vienna and Denmark's cession of the Duchies of Schleswig (except for the island of Ærø, which remained Danish), Holstein and Saxe-Lauenburg to Prussia and Austria.