In foreign policy, Napoleon III aimed to reassert French influence in Europe and around the world. In Europe, he allied with Britain and defeated Russia in the Crimean War (1853–1856). His regime assisted Italian unification by defeating the Austrian Empire in the Franco-Austrian War and later annexed Savoy and Nice through the Treaty of Turin as its deferred reward. At the same time, his forces defended the Papal States against annexation by Italy. He was also favourable towards the 1859 union of the Danubian Principalities, which resulted in the establishment of the United Principalities of Moldavia and Wallachia. Napoleon III doubled the area of the French overseas empire with expansions in Asia, the Pacific and Africa. On the other hand, the intervention in Mexico, which aimed to create a Second Mexican Empire under French protection, ended in total failure. From 1866, Napoleon III had to face the mounting power of Prussia as its Chancellor Otto von Bismarck sought German unification under Prussian leadership. In July 1870, Napoleon III reluctantly declared war on Prussia after pressure by the public. Without allies and with inferior military forces, the French Army was rapidly defeated as Napoleon III was captured at Sedan. He was swiftly dethroned and the Third Republic was proclaimed in Paris. He went into exile in England, where he died in 1873.