July 12, 1858 and July 6, 1859
Napoleon III secretly met with Cavour of Piedmont-Sardinia in the spa town of Plombieres on July 12, 1858. During this meeting, they made an agreement that became known as the Treaty of Plombieres. The treaty gave Piedmont-Sardinia access to French troops to help with the war they would be starting with Austria (Austro-Sardinian War) and in exchange France would receive the territories of Nice and Savoy. These two territories had been held by France in the past but were returned to Sardinia by the Congress of Vienna.
After two battles with Austria, battles that the French won but lost many men, the threat of Prussia joining with Austria and Austria’s need to get out of the war, Napoleon III started to have second thoughts about his treaty with Cavour. This led Napoleon III to meet with Austria behind Cavour’s back. Napoleon III signed an armistice, Treaty of Villafranca, with Austria on July 6, 1859 and ceded his claim to Nice and Savoy. The Treaty of Villafranca outraged Cavour and led him to resign from his post.