Carbonari, a secret society was formed by people to liberate Italy from clutches of foreigners. Rulers of Naples and Piedmont also encouraged liberal tendencies. But these efforts were curbed by Metternich.
French revolutions of 1830 and 1848 sparked feelings of liberation, but the smaller states couldn’t coordinate and Austria again suppressed movements and movement was divided into – moderates and revolutionaries (under Mazzini).
Mazzini joined Carbonari at young age. He formed ‘Young Italy’ movement to liberate Italy on line of Carbonari and setup Republic which was destroyed by Napoleon lll. He tried to bring unification multiple times by revolts especially in Milan and Lombardi, but failed. The failure of revolutionary uprisings both in 1831 and 1848 meant that the mantle now fell on Sardinia- Piedmont under its ruler King Victor Emmanuel II to unify the Italian states through war. He was, however, the ideological spirit behind unification and major spirit behind nationalism and made unification a popular cause.
By 1848, it became apparent that without dislodging Austria unification will be difficult. Cavour, the PM of Sardinia took up this task. Like Bismarck, he took up the task of economic and military strengthening of Piedmont. He joined Crimean war to support England and France to win their support in it cause to liberate Lombardi and Venice from clutches of Austria. Later he tied up with Napoleon lll of France to fight Austria. On excuse of rebellion in Sardinia, both waged war against Austria. However, the victory was incomplete as only Sardinia could be acquired (Napoleon became wary of Sardinia’s rising clout and hence made peace with Austria to check it). Cavour, then moved South and took advantage of revolt of inhabitants of Sicily.
Garibaldi helped in success of revolt and later in a plebiscite it was later merged with Sardinia- Piedmont in 1860. When Prussia under Bismarck attacked Austria, Venice too became a part of Sardinia. Finally, Rome, which under France promoted Pope’s control, became part after Prussia France war. By 1871, unification was complete.