Cinco de Mayo
Cinco de Mayo is NOT Mexican Independence Day—that's September 16. Cinco de Mayo, the 5th of May, celebrates an incredible victory by native Mexican soldiers over the imperialist French who tried to rule them way back in 1862.
The French wanted to collect their debts from Mexico and, rather than making a deal with Mexican government, decided to put into power a new French emperor, Maximilian. Most native Mexicans were furious.