Why did Austria go to war with Prussia in 1866?

The war between Austria and Prussia in 1866, known as the Seven Weeks’ War, was primarily driven by Prussia’s deliberate challenge to Austria for leadership of the German Confederation.

Under the guidance of Otto von Bismarck, Prussia sought to unify Germany under its own Hohenzollern dynasty and exclude Austria from German affairs. While the two powers had previously cooperated to defeat Denmark in 1864, tensions escalated over the joint administration of the duchies of Schleswig and Holstein. Bismarck utilized this administrative dispute as a pretext to provoke conflict.12

For Franz Joseph, the war became inevitable as Prussia increasingly refused to recognize Austria as the leading German power. Despite Franz Joseph’s attempts to navigate the crisis, including a failed effort to avoid simultaneous conflict with Italy, the war resulted in a decisive Prussian victory at the Battle of Königgrätz. This defeat ultimately sealed Austria’s expulsion from Germany and led to the establishment of the Prussian-dominated North German Confederation.123