Political map of Europe & the Mediterranean 24 June 1866 (End of the German Confederation): Prussia responded swiftly to the German Federal Diet's vote for mobilization (Austro-Prussian War), declaring the German Confederation (German Confederation) at an end and occupying Austria's northern allies. Meanwhile Italy joined the war against Austria (Third Italian War of Unification) and launched an invasion of Venitia, only to be beaten back at Custoza (Battle of Custoza (1866)) just days later.