On this day in 1866 Italy and Prussia allied against the Austrian Empire.
Austria was defeated by the Prussian army in the Austro-Prussian War of 1866 in the north, but resisted on land and sea against the Italians in the south. Venetia and Mantovano joined Italy. Austria renounced its membership of the German Confederation.
After this military and political disaster, the nationalities made new demands, and eventually a compromise was reached with the Hungarians in 1867. The Austrian Empire was transformed into the Austro-Hungarian Empire by the Austro-Hungarian Compromise of 1867, which granted Hungary and the Hungarian lands equal status to the rest of Austria as a whole. In June 1867, Franz Joseph I was crowned King of Hungary. It should be noted that the K.u.K. (German for Imperial and Royal) is not related to this fact (the name “Imperial and Royal” was born in 1745 where the “royal” part meant the Apostolic Kingdom of Hungary).