In 1853 Mexican president Santa Anna unintentionally ushered in a new era of liberal political consolidation and economic reform by triggering a backlash against his sale of territory along the northern border to the United States. Many Mexicans saw his act as a betrayal of the nation and threw their support behind a new generation of liberal leaders. Beginning with the presidency of Ignacio Comonfort (pres. 1855–1858), these liberals carried out sweeping legal and economic changes called La Reforma, or “the reform.”

Liberal reformers sought to make all individuals equal under the law and established property ownership as a basic right and national goal. The first major step in La Reforma was the Juarez Law (1855), which abolished legal privileges for military officers and members of the clergy. An even more consequential measure, the Lerdo Law (1856), banished another legacy of colonialism: “corporate lands,” meaning lands owned by groups or institutions, such as the Catholic Church, rather than by individual property owners. Liberals wanted to redistribute church-owned lands among farmers who would own them as private parcels and who would profit from working them efficiently.

These liberal reforms triggered a backlash from conservative landowners and the church. When liberals enshrined these laws and other reforms in a new constitution ratified in 1857, the Catholic Church threatened to excommunicate anyone who swore allegiance to it. Conservatives revolted, triggering a civil war called the Wars of Reform (1857–1861). Liberal forces led by Benito Juárez defeated the conservatives, who then conspired with French emperor Napoleon III to invite a French invasion of Mexico in 1862. French victory led to the installation of Napoleon III’s Austrian cousin Maximilian of Habsburg as emperor of Mexico.

The deposed Juárez led a guerrilla war against the French troops backing Maximilian. Juárez’s nationalists prevailed, restored Mexico’s republic, and executed Maximilian. Conservatives had been completely discredited: they had conspired with another country to install a foreign leader through a military invasion.