Victor Emmanuel II of Savoy had been crowned King of Italy on 17 March 1861 but did not control Venetia or the much reduced Papal States. The situation of the Irredente (a later Italian term for part of the country under foreign domination, literally meaning un-redeemed) was an unceasing source of tension in the domestic politics of the newly created Kingdom, as well as being a cornerstone of its foreign policy.
The first attempt to seize Rome was orchestrated by Giuseppe Garibaldi in 1862. Confident in the King's neutrality, he set sail from Genoa to Palermo. Collecting 1,200 volunteers, he sailed from Catania and landed at Melito, in Calabria, on 24 August to reach Mount Aspromonte, with the intention to travel northwards up the peninsula 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 increasing discord between Austria and Prussia over the German Question turned into open war in 1866, offering Italy an occasion to capture Venetia. On 8 April 1866 the Italian government signed a military alliance with Prussia, through the mediation of Emperor 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 perceived naval superiority, the Italians planned to threaten the Dalmatian coast and seize Trieste.