Mexico’s independence day is September 16, not May 5.
In the aftermath of the Mexican-American War (the aftermath of the United States’ decision that they would take Texas, thank you very much) and the Reform (Mexican Civil) War, Mexico’s dire financial resulted the country suspending debt payments to foreign lenders. Britain, Spain and France responded by sending naval forces to Veracruz to demand their money. Britain and Spain negotiated a settlement and left. France executed a different strategy.
French forces conquered Veracruz in 1861 and, with President Juarez and the government in retreat, marched toward Mexico City. Beleaguered and greatly outnumbered, Mexican forces decisively defeated the French at Puebla. Although France came back a year later with quadruple the troops to retake the country, the battle at Puebla instilled pride and patriotism among the Mexican populace.
The French victory was short-lived. With Napoleon III’s attention turned to more imminent threats, like the impending Franco-Prussian War, France withdrew three years later and Benito Juárez established a new government.
Cinco de Mayo has been celebrated in California since 1863 and has since become a significant date across the U.S. Here in Portland Cinco de Mayo begins on the 3rd and takes over Waterfront Park downtown for three days of music, dancing, food and general merriment.