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.'
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 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.