Since August 1859, the pro-Piedmontese regimes of Tuscany, Parma, Modena and the Papal Legations entered into a group of military treaties. On 7 November 1859, they elected Eugenio Emanuele di Savoia-Carignano as their regent. However, King Victor Emmanuel II of Savoy, who was allied to France which claimed a counterpart, refused to endorse the election, and sent Carlo Bon Compagni instead as the Governor General of Central Italy, who was responsible for the diplomatic and military affairs of the states.
On 8 December 1859, Parma, Modena and the Papal Legations were incorporated into the Royal Provinces of Emilia. After plebiscites were held in March 1860, and France was granted Nice and Savoy, the territory was formally annexed to Piedmont-Sardinia.