1901 poster for Cinco de Mayo: “May 5, 1862 and the siege of Puebla”
Events leading to the Battle of Puebla
Cinco de Mayo has its roots in the French occupation of Mexico, which took place in the aftermath of the Mexican–American War of 1846–48 and the 1858–61 Reform War. The Reform War was a civil war and it pitted Liberals (who believed in separation of church and state and freedom of religion) against the Conservatives (who favored a tight bond between the Roman Catholic Church and the Mexican State). These wars left the Mexican Treasury nearly bankrupt. On July 17, 1861, Mexican President Benito Juárez issued a moratorium in which all foreign debt payments would be suspended for two years. In response, France, Britain, and Spain sent naval forces to Veracruz to demand reimbursement. Britain and Spain negotiated with Mexico and withdrew, but France, at the time ruled by Napoleon III, decided to use the opportunity to establish a Latin empire in Mexico that would favor French interests, the Second Mexican Empire.
Late in 1861, a well-armed French fleet stormed Veracruz, landing a large French force and driving President Juárez and his government into retreat. Moving on from Veracruz towards Mexico City, the French army encountered heavy resistance from the Mexicans close to Puebla, at the Mexican forts of Loreto and Guadalupe. The 6,000-strong French army[note 1] attacked the much smaller and poorly equipped Mexican army of 2,000.[note 2] Yet, on May 5, 1862, the Mexicans managed to decisively crush the French army, then considered “the premier army in the world”.
The victory represented a significant morale boost to the Mexican army and the Mexican people at large. In the description of The History Channel, “Although not a major strategic win in the overall war against the French, Zaragoza’s success at Puebla represented a great symbolic victory for the Mexican government and bolstered the resistance movement.” As Time magazine remarked, “The Puebla victory came to symbolize unity and pride for what seemed like a Mexican David defeating a French Goliath.” It helped establish a much-needed sense of national unity and patriotism.
Events after the battle
The Mexican victory, however, was short-lived. A year later, with thirty thousand troops, the French were able to defeat the Mexican army, capture Mexico City, and install Emperor Maximilian I as ruler of Mexico. The French victory was short-lived, lasting only three years, from 1864 to 1867. By 1865, “with the American Civil War now over, the U.S. began to provide more political and military assistance to Mexico to expel the French”. Upon the conclusion of the U.S. Civil War, Napoleon III, facing a persistent Mexican guerilla resistance, the threat of war with Prussia, and “the prospect of a serious scrap with the United States”, retreated from Mexico starting in 1866. The Mexicans recaptured Mexico City, and Maximilian I was apprehended and executed, along with his Mexican generals Miramón and Mejía, in the Cerro de las Campanas, Querétaro. “On June 5, 1867, Benito Juarez finally entered Mexico City where he installed a legitimate government and reorganized his administration.”
The Battle of Puebla was important for at least two reasons. First, although considerably outnumbered, the Mexicans defeated a much better-equipped French army. “This battle was significant in that the 4,000 Mexican soldiers were greatly outnumbered by the well-equipped French army of 8,000 that had not been defeated for almost 50 years.”  [note 3] Second, since the Battle of Puebla, no country in the Americas has subsequently been invaded by any other European military force.[note 4]