In the 1840s, post-Napoleonic Italy was ’a geographical expression’--not a country, but a patchwork of states. The north (Savoy/Piedmont, and Venice ) was ruled by Austria-Hungary, and most of the minor central states were more or less clients of Austria. From Naples, a Spanish-descended Bourbon monarchy ruled the south--’the Two Sicilies’, i.e. the southern ’boot’ of the mainland, and the island. The European ’Year of Revolutions’, 1848, saw popular uprisings against the regimes all over the peninsula. These were eventually crushed (First War of Independence, 1848–49); but they left King Victor Emmanuel of Savoy/Piedmont--and his able minister Cavour--determined to liberate and unify the country, while royal authority in the Kingdom of the Two Sicilies was left deeply unpopular.
Savoy/Piedmont endeavored to strengthen the relationship with France and Britain, by sending troops to fight alongside them in the Crimean War, 1854-56 and, as a result, it was actively supported by a French army in the Second War of Independence (1859), when the battles of Magenta and Solferino freed most of the north from Austrian rule. In the south, Garibaldi’s ’Redshirts’ led a successful rising against the Kingdom of the Two Sicilies (1860). Eventually the south voted to join the north in a unified kingdom (February 1861); nevertheless, northern troops had to enforce this by a ruthless occupation during the 1860s--a little-known campaign. Only Austrian-occupied Venice and French-sponsored Rome and the Papal States remained independent. In 1866 Italy sided with Prussia against Austria (Third War of Independence), and consequently gained Venice after the Prussian victory. In 1870 Italian royal troops finally occupied Rome.