Austro-Prussian War
The pretext for the conflict was found in the dispute between Prussia and Austria over the administration of Schleswig-Holstein, which the two of them had conquered from Denmark and agreed to jointly occupy at the end of the Second Schleswig War in 1864. When Austria brought the dispute before the German Diet and also decided to convene the Diet of Holstein, Prussia declared that the Gastein Convention had thereby been nullified and invaded Holstein. When the German Diet responded by voting for a partial mobilization against Prussia, Bismarck claimed that the German Confederation was ended. Crown Prince Frederick "was the only member of the Prussian Crown Council to uphold the rights of the Duke of Augustenburg and oppose the idea of a war with Austria which he described as "fratricide"". Although he supported unification and the restoration of the medieval empire, "Fritz could not accept that war was the right way to unite Germany."
Austria–Prussia rivalry
Maria Theresa, still chafing under the loss of "the most beautiful gem of my crown", took the opportunity of the breathing space to implement several civil and military reforms within the Austrian lands, like the establishment of the Theresian Military Academy at Wiener Neustadt in 1751. Her capable state chancellor, Prince Wenzel Anton of Kaunitz, succeeded in the Diplomatic Revolution of 1756, allying with the former Habsburg nemesis France under King Louis XV in order to isolate Prussia. Frederick, however, had completed the "stately quadrille" by the conclusion of the Treaty of Westminster with Great Britain. He again took action by a preemptive war, invading Saxony and opening a Third Silesian War (and the wider Seven Years' War).