Third Italian War of Independence The Third Italian War of Independence was a conflict which paralleled the Austro - Prussian War , and was fought between the Kingdom of Italy and the Austrian Empire . Background . Victor Emmanuel II of Savoy had been crowned King of Italy on March 17 , 1861 , his reign did not control Venetia and Lazio . The situation of the " Irredente " ( a later Italian term for part of the country under foreign domination , literally meaning " un - redeemed " ) created an unceasing state of tension for the inner politics of the newly created Kingdom , as well as being a cornerstone of its foreign policy . A first attempt to capture Rome was that of 1862 by Giuseppe Garibaldi . Confiding in the King ' s neutrality , he had set sail from Genoa to Palermo . Collecting 1 , 200 volunteers , he moved from Catania and landed at Melito , in Calabria , on August 24 to reach the Aspromonte , with intention to climb the peninsula up to Rome . The Piedmontese general Enrico Cialdini , however , sent a division under colonel Pallavicino to stop the volunteer army . Garibaldi himself was wounded in the ensuing battle , and taken prisoner along with his men . The growing divergences between Austria and the growing Prussia ' s predominance in Germany turned into an open war in 1866 , offering Italy an occasion to regain Venetia . On April 8 , 1866 the Italian government signed a military alliance with Prussia , through the mediation of Napoleon III of France . Italian armies , led by general Alfonso Ferrero La Marmora , were to engage the Austrians on the southern front . Simultaneously , taking advantage of their naval superiority , the Italians threatened the Dalmatian coast , forcing Austria to move part of its forces there from the central European front . Italian preparedness . At the outbreak of the war , the Italian military situations was hampered by the following factors : Italian invasion . Prussia began hostilities on June 16 , 1866 by attacking several German principates allied with Austria . Three days later Italy declared war on Austria , starting the military operations on June 23 . The Italian forces were divided into two armies : the first , under La Marmora himself , was deployed in Lombardy , west of the Mincio River , aiming toward the powerful Quadrilatero fortress of the Austrians ; the second , under Enrico Cialdini , in Romagna , south of the Po River , aiming toward Mantua and Rovigo . La Marmora moved first through Mantua and Peschiera del Garda , but was defeated at the Custoza on June 24 . Cialdini , however , did not act offensively for the entire first part of the war , conducting only several shows and even failing to besiege the Austrian fortress of Borgoforte , south to the Po . Custoza marked a general arrest of operations , as the Italians decided to reorganize for fear of an Austrian counter - offensive . The Austrians indeed profited from the situation to raid Valtellina and Val Camonica ( battle of Vezza d ' Oglio ) . The general course of the war , however , was to turn in Italy ' s favor thanks to Prussian victories in the north , especially that of Königgrätz on July 3 , 1866 . The Austrians were compelled to move one of their three army corps deployed in Italy to Vienna , concentrating on the defense of Trentino and Isonzo . New Italian offensive . On July 5 the Italian government received news of a mediation effort by Napoleon III for a settlement of the situation , which would allow Austria to receive favourable conditions from Prussia , and , in particular , to maintain Venice . The situation was embarrassing for Italy , as its forces had failed to obtain any relevant military success on the field . As the Austrians were redeploying troops to Vienna , La Marmora was solicited to take advantage of the numeric superiority , score a good victory , and thus improve the conditions for Italy . On July 14 , during a council of war held in Ferrara , the new conduct of the war was decided , according to the following points : Cialdini crossed the Po and occupied Rovigo ( July 11 ) , Padua ( July 12 ) , Treviso ( July 14 ) , San Donà di Piave ( July 18 ) , Valdobbiadene and Oderzo ( July 20 ) , Vicenza ( July 21 ) and finally Udine , in Friuli ( July 22 ) . In the meantime Garibaldi ' s volunteers had pushed forward from Brescia towards Trento ( see Invasion of Trentino ) fighting victoriously at the battle of Bezzecca of July 21 . These victories were however obscured by the unexpected defeat of the Italian Navy at the Battle of Lissa ( July 20 , 1866 ) . On August 9 , upon receiving from the King the order to retreat from the newly conquered positions , Garibaldi complied with his famous " Obbedisco ! " ( " I obey ! " ) telegram , and retreated from Trentino . The ceasing of hostilities was marked by the Armistice of Cormons signed on August 12 , followed by the Treaty of Vienna of October 3 , 1866 . Aftermath . The terms included the cession of Venetia ( with Mantua and western Friuli ) to France ( which ceded it to Italy ) and of the Iron Crown ( worn by the old Lombard Kings of Italy and by the Holy Roman Emperors , as well as by Napoleon Bonaparte himself ) . The " redente " ( " released " ) lands were annexed to Italy through a plebiscite held on October 21 and 22 of 1866 . This left Rome and its Patrimony of St Peter ( now Lazio ) outside the Kingdom of Italy , until the " Capture of Rome " in September 1870 and the subsequent plebiscite approving its unification with the rest of Italy . References . This article is a translation of an article in the Italian - language Wikipedia .