After fall of Santa Ana following in the late 1840s, Mexico entered a period of instability characterized by conflict between the Conservatives, supported by the military and the Church, and the Liberals, who favored reducing the power of those institutions and expanding rights to a larger portion of Mexico's population. The Liberals, under Benito Juarez, took power in 1855 and passed a number of reforms, culminating in the Constitution of 1857, which provided equal rights to all citizens and dramatically reducing the power of the Catholic Church.

In reaction to this, the Conservatives revolted against the government, started the Reform War that lasted until 1861. Juarez and the Liberals were ultimately triumphant, but the economy of Mexico was severely damaged. In order to rebuild the country, Juarez cancelled the payment of the Mexican debt to the major European powers. As a result, Britain, France and Spain formed a coalition to invade Mexico. However, Napoleon III wanted more than just a restarting of debt payments. Rather, he wanted to insure that Europe had a friendly market for goods in Latin America, and also easy access to Mexican silver. Once the British and Spanish found out about these plans, they pulled out of the coalition, leaving France to attack Mexico on its own.