An evaluation of the reasons why unification was achieved in Italy, by 1870

Diplomatic and International Factors

French aid to Piedmont: The support of Napolean III was a significant factor. His unexpected help to the Piedmont-Sardinian State against Austria guided Italy closer to unification.
The role of Bismarck: The Prussian Chancellor, Otto von Bismarck’s policies, particularly in taking on Austria in the Austro-Prussian War of 1866, concluded with Venetia joining Italy.
Withdrawal of the French in 1870: The withdrawal of French troops from Rome due to the Franco-Prussian war facilitated the invasion of Rome by Italian forces, culminating in the final act of unification.

Cavour’s diplomacy: The astute political and diplomatic skills of Camillo di Cavour, the prime minister of Piedmont, were instrumental in attracting allies and isolating opponents like Austria.
Contributions of Garibaldi: The military exploits of Garibaldi, especially his capture of Sicily and Naples, significantly accelerated the progress towards unification.

Piedmontese military strength: Piedmont’s efficient army under General Alfonso La Marmora played a crucial part in acquiring territories such as Lombardy and later Rome.
Role of the Red Shirts: Garibaldi’s volunteer force’s successful campaigns led to the unification of most of southern Italy under the umbrella of the Kingdom of Piedmont-Sardinia.

Impact of revolts: Regional revolts and uprisings, although often crushed, kept the unification issue alive and pressured leaders to push for a unified state.
Mazzini and Young Italy: The ideological groundwork laid by Giuseppe Mazzini and his movement Young Italy provided the essential nationalist sentiment and desire for unity.

Increased socio-political consciousness: By the mid-19th century, a more knowledgeable and politically aware Italian society desired unification as a means of stability and progress.
King Victor Emmanuel: His role as a figurehead for unification cannot be ignored. His acceptance as king by the Italian territories was crucial in creating a unified state.