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."
Seven Years' War
Britain now threatened to withdraw its subsidies if Frederick did not consider offering concessions to secure peace. As the Prussian armies had dwindled to just 60,000 men and with Berlin itself about to come under siege, the survival of both Prussia and her King was severely threatened. Then on 5 January 1762 the Russian Empress Elizabeth died. Her Prussophile successor, Peter III, at once ended the Russian occupation of East Prussia and Pomerania (see: the Treaty of Saint Petersburg (1762)) and mediated Frederick's truce with Sweden. He also placed a corps of his own troops under Frederick's command. Frederick was then able to muster a larger army, of 120,000 men, and concentrate it against Austria. He drove them from much of Silesia, while his brother Henry won a victory in Saxony in the Battle of Freiberg (29 October 1762). At the same time, his Brunswick allies captured the key town of Göttingen and compounded this by taking Cassel.