The second French intervention in Mexico (Spanish: segunda intervención francesa en México), also known as the Second Franco-Mexican War (1861–1867), was a military invasion of the Republic of Mexico by the French Empire of Napoleon III, purportedly to force the collection of Mexican debts in conjunction with Great Britain and Spain. Mexican conservatives supported the invasion, since they had been defeated by the liberal government of Benito Juárez in a three-year civil war. Defeated on the battlefield, conservatives sought the aid of France to effect regime change and establish a monarchy in Mexico, a plan that meshed with Napoleon III's plans to re-establish the presence of the French Empire in the Americas. Although the French invasion displaced Juárez's Republican government from the Mexican capital and the monarchy of Archduke Maximilian was established, the Second Mexican Empire collapsed within a few years. Material aid from the United States, whose four-year civil war ended in 1865, invigorated the Republican fight against the regime of Maximilian, and the 1866 decision of Napoleon III to withdraw military support for Maximilian's regime accelerated the monarchy's collapse.
The intervention came as a civil war, the Reform War, had just concluded, and the intervention allowed the Conservative opposition against the liberal social and economic reforms of President Juárez to take up their cause once again. The Catholic Church, conservatives, much of the upper-class and Mexican nobility, and some indigenous communities invited, welcomed and collaborated with the French empire to install Maximilian as Emperor of Mexico. However, there was still significant support for republicanism in Mexico. Mexican society was most resistant to European models of governance, including monarchies, during and after the French intervention. The emperor himself however proved to be of liberal inclination and continued some of the Juárez government's most notable measures. Some liberal generals defected to the empire, including the powerful, northern governor Santiago Vidaurri, who had fought on the side of Juárez during the Reform War.
