The 1866 Treaty of Vienna was an agreement signed on the 3rd of October and later ratified on the 12th by the Kingdom of Italy and the Austrian Empire that concluded the hostilities of the Third War of Italian Independence, a theatre of concurrent Austro-Prussian War. The treaty confirmed the terms of the August 12th Armistice of Cormons, resulting in the transfer of Venetia and most of Friuli to the French Empire, who then gave the region to Italy after the consent of the inhabitants through a referendum. This represented the final division of the Habsburg ruled Kingdom of Lombardy–Venetia, as the Lombard half had been ceded to the Kingdom of Sardinia in the earlier 1859 Treaty of Zurich. The treaty forced the Austrian government to recognise the sovereignty of the new Italian Kingdom. This coupled with the Prussian defeat of Austria made apparent the decline of the Habsburg monarchy as a great power. The treaty also signalled the rise of Italy as the sixth great power of Europe. Background Since 1848 Italian nationalist societies and the Kingdom of Piedmont-Sardinia had been trying to unify the post-Napoleonic Italian states into a single Italian nation. The main obstacle to Italian Unification was the Habsburg monarchy, which directly or indirectly controlled much of Italy and was actively invested in keeping Italy divided. To overcome Austrian military might Piedmont (then Italy from 1861) would need to rely on foreign intervention by other European nations to overcome Austria. To this end the Piedmontese Prime Minister, Camillo Benso, Count of Cavour, forged an alliance with France, agreeing to turn over the French speaking provinces of Savoy and Nice to France in exchange for military support against Austria. This support would be vital to Italian success in the Second War of Italian Unification, which resulted in the Austrians ceding Lombardy to Piedmont. In mid-June 1866 war broke out between Austria and Prussia over the administration of Schleswig and Holstein and the future of the German Confederation. Italy took advantage of the situation by siding with Prussia in the conflict, declaring war on Austria on 20 June. The Italian government hoped that the ongoing Austro-Prussian campaign would allow their armies to flank the Austrian forces, seizing Venice, Friuli, Trentino, and Trieste with little difficulty. Austrian forces defeated the Italian Army at the Battle of Custoza and the Italian Navy at Battle of Lissa; however, in the meantime,