PLOMBIÈRES, CONGRESS OF. - The personal policy of Napoleon III, tending on the one hand to ensure the triumph of the principle of nationality in Italy and desirous on the other of guaranteeing particular advantages to France and to his own family, led in 1858 to the Conference of Plombières, a spa town in the Vosges. There the Emperor of the French met secretly with Cavour and discussed the possibility of a military alliance with Piedmont against Austria.
The meeting, which took place on 21 July, lasted several hours. Before proceeding to examine the individual problems, Napoleon III set forth his precondition against any achievement of Italian unity by revolutionary means (the memory of Felice Orsini's attempt on his life was recent), thereby implicitly placing himself on the political platform of Count Cavour, which tended to "diplomatize" the movement for Italian independence. To this declaration the Emperor of the French added other reservations, namely that he could not consent to the dethronement of the Bourbons in the Kingdom of the Two Sicilies nor to that of the Pontiff in the Papal States, so as not to create difficulties in relations with Russia and not to alienate the support of French Catholics. Cavour accepted these reservations, but nevertheless countered to Napoleon the possibility of proceeding with the annexation of the Legations, the Marches and Umbria, while preserving for the Pope sovereignty over Rome and the Patrimony of St. Peter. After this agreement on the limits of French support for the cause of Italian independence, Napoleon declared himself in favor of a settlement of the status of the peninsula with a kingdom of northern Italy under the scepter of the Savoys, comprising besides Piedmont also Parma, Modena, the Lombardo-Venetian Kingdom and the Legations. Tuscany, together with the Marches and Umbria, was in turn to constitute a kingdom of central Italy. The whole peninsula, together with the Kingdom of the Two Sicilies, would furthermore constitute a confederation, whose presidency would be conferred on the Pontiff. In compensation the Kingdom of Sardinia would cede Savoy to France and Victor Emmanuel II would grant his daughter Maria Clotilde in marriage to his cousin Jerome. The Conference of Plombières is of particular importance for the history of the papacy and for the movement of Italian independence and unity: without it the second war of independence of 1859 would never have broken out, and with it the critical phase of the Roman Question opened.