The unification of Italy as a nation state occurred between 1815-1870, one of the last European countries to unify. Before that Italy was a collection of small states subject to foreign powers.
In 1814, Italy had 12 states and was dominated by Austria in the north and center. The opposition of the Italian to Austrian rule manifested itself in an increasingly strong sentiment in favor of national unity and independence, whose first symptom was the birth of a network of secret societies that played a vital role in the course of revolutions 1820, strongly suppressed by Austria.
Between 1820-1848 occur several revolts led by secret societies like the Carbonari and Young Italy movement that were harshly suppressed and did not obtain significant results. During this period, the revolutionaries proclaim at least three republics. After the revolutionary wave, the more traditional parties grew , subsequently promoting Italian unity, in non- democratic basis, under the aegis of the Kingdom of Sardinia. The defeat of the revolutionaries led to the restoration of absolutism in almost all Italian states.
Between 1848 and 1866 the armies of the Kingdom of Sardinia and the Austrian Empire fought three wars that with alternating successes have led to the release of most of the northern Italian peninsula from Austrian rule.
It was between the years 1859 to 1860 continuing the process of unification which concluded with the declaration of the existence of the Kingdom of Italy. In the struggle over the future structure of Italy, the monarchy supported by conservative liberals, succeeded in 1861 when it formed the Nation-State, outweighing supporters left, Republican and Democratic. The unification was completed with the annexation of Rome before the capital of the Papal States in 1870 and being transformed into the capital of the kingdom which was forming.
In 1871 he was offered as an indemnity compensation to the Pope and the commitment to keep him as head of the Vatican State, a district of Rome where was the seat of the Church. Pope Pius IX, aware of his influence on Italian Catholics and desiring to preserve the power of the Church declined the offer and declared himself voluntary prisoner of the Italian State. Moreover, forbade Italian Catholics to vote in elections of the new kingdom. This vexed question of disputes between the State and the Church, called Roman Question, only ended in 1929, when the fascist dictator Benito Mussolini, requiring the support of the Catholic Church and signed with Pope Pius XI the Concordat of St. John Lateran. By this treaty, signed up an agreement by which created the Vatican State. Italy became Republic only in June 2, 1946 after a plebiscite.