Second war of Schleswig also known as Danish war or Danish-Prussian war in 1864 was fought between Denmark and Prussia. Prussia was supported by Austria, and both of them were acting on behalf of the German Confederation.

When the government in Copenhagen proclaimed Schleswig an integral part of the Danish state in 1863, German nationalists were outraged. King Wilhelm I proposed to Emperor Francis Joseph that the two leading powers of the German Confederation, Prussia and Austria, should occupy the duchies of Schleswig and Holstein in order to prevent the violation of the 1460 Treaty of Ripen that had guaranteed their status as twin-duchies. Afraid to let the Prussians act on their own, the emperor agreed, and in 1864 there was a brief war against Denmark that demonstrated the strength of the reorganized army of the Hohenzollerns. Danish hopes for Swedish assistance proved illusory, and by the Peace of Vienna (October 30) the duchies became the joint possession of Prussia and Austria.

See also

• Schleswig-Holstein
• Prussia
• First war of Schleswig
• Seven Weeks War