Emperor of the French (1852–1871). A nephew of Napoleon I, he led the Bonapartist opposition to Louis Philippe and became president of the Second Republic (1848). After proclaiming himself emperor (1852), he instituted reforms and rebuilt Paris. His successful imperialist ventures were overshadowed by a failed campaign in Mexico (1861–1867) and the Franco-Prussian War (1870–1871), which resulted in his deposition.