What Is Cinco De Mayo, Really?
Some believe that Cinco De Mayo is Mexican Independence day, which it is not. Some believe that even though Cinco de Mayo is not an American holiday, it should be. Mexico first declared it's independence from Spain on September 15, 1810 and it took until 1821 to get all of the Spanish soldiers out of Mexico once and for all. The French, along with Spanish and English troops, landed in Mexico in December of 1861 to collect Mexican debts from the new Mexican government led by Benito Juarez. England and Spain made their deals and left Mexico quickly, but the French, under Napoleon had very different plans.
It was May 5, 1862 that the Mexican Army of 4,000 smashed Napoleon's army of 8,000 at Puebla, Mexico. Union forces for the United States under the command of General Phil Sheridan assisted the Mexican Army by supplying weapons and ammunition to fight the French. Some have argued that the French had motivations that went beyond Mexico. Keep in mind the U.S. was in the midst of the Civil War at the time and Napoleon III was helping the Confederate forces and a victory in Mexico would essentially break up the American Union.
Mexico's victory over the French only strengthened the American Union, which allowed for the Union Army to crush the Confederates at Vicksburg and Gettysburg effectively ending the Civil War just 14 months after Puebla.
California has been celebrating Cinco De Mayo continuously since 1863. The rest of the U.S. followed suit in the early 1940s making it a bigger deal here than it is in Mexico where it is celebrated, but not as a national holiday. It is only an official holiday in the State of Puebla.
In 1941, when the Japanese bombed Pearl Harbor, to show their gratitude for our help against the French, thousands of Mexicans crossed the U.S. Border to join the U.S. Armed Forces against Japan.