The Second Italian War of Independence, also called the Franco-Austrian War, the Austro-Sardinian War or Italian War of 1859 (; ), was fought by the Second French Empire and the Savoyard Kingdom of Sardinia against the Austrian Empire in 1859 and played a crucial part in the process of Italian Unification. A year prior to the war, in the Plombières Agreement, France agreed to support Sardinia's efforts to expel Austria from Italy in return for territorial compensation in the form of the Duchy of Savoy and the County of Nice. The two states signed a military alliance in January 1859. Sardinia mobilised its army on 9 March 1859, and Austria mobilized on 9 April. On 23 April, Austria delivered an ultimatum to Sardinia demanding its demobilization. Upon Sardinia's refusal, the war began on 26 April. Austria invaded Sardinia three days later, and France declared war on Austria on 3 May. The Austrian invasion was stopped by the arrival of French troops in Piedmont that had begun in late April. The Austrians were defeated at the Battle of Magenta on 4 June and pushed back to Lombardy, where the Franco-Sardinian victory at the Battle of Solferino on 24 June resulted in the end of the war and the signing of the Armistice of Villafranca on 12 July. Austria ceded Lombardy to France, which, in turn, gave it to Sardinia. Exploiting the collapse of Austrian power in Italy, Sardinia annexed the United Provinces of Central Italy, consisting of the Grand Duchy of Tuscany, the Duchy of Parma, the Duchy of Modena and Reggio and the Papal Legations, on 22 March 1860. Two days later, Sardinia ceded Savoy and Nice to France at the Treaty of Turin as compensation for its assistance. Background The Piedmontese, following their defeat by Austria in the First Italian War of Independence, recognized their need for allies. That led Prime Minister Camillo Benso, Count of Cavour to attempt to establish relations with other European powers, partially through Piedmont's participation in the Crimean War. In the peace conference at Paris after the Crimean War, Cavour attempted to bring attention to efforts for Italian unification. He found Britain and France to be sympathetic but refusing to go against Austrian wishes, as any movement towards Italian independence would threaten Austria's territory of Lombardy–Venetia. Private talks between Napoleon III and Cavour after the conference identified Napoleon as the most likely candidate to