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."
History of Austria
Over the next three years Austria, whose foreign policy was now directed by Philipp Stadion, attempted to maintain peace with France, avoiding the War of the Fourth Coalition (1806–1807) but obliged to do France's bidding. The overthrow of the Spanish Bourbons in 1808 was deeply disturbing to the Habsburgs, who rather desperately went to war once again in 1809, the War of the Fifth Coalition this time with no continental allies, but the United Kingdom. Stadion's attempts to generate popular uprisings in Germany were unsuccessful, and the Russians honoured their alliance with France, so Austria was once again defeated at the Battle of Wagram, although at greater cost than Napoleon, who had suffered his first battlefield defeat in this war, at Aspern-Essling, had expected. However Napoleon had already re-occupied Vienna. The terms of the subsequent Treaty of Schönbrunn were quite harsh. Austria lost Salzburg to Bavaria, some of its Polish lands to Russia, and its remaining territory on the Adriatic (including much of Carinthia and Styria) to Napoleon's Illyrian Provinces. Austria became a virtual subject state of France.