152 years ago . . . In 1862, CINCO DE MAYO, the Mexican army scored an upset victory over the invading French army at the Battle of Puebla.

Even though the Mexicans held off the French that day, they didn't win their war.  About a year later, the French successfully occupied Mexico City.  They didn't leave until the U.S. strongly pressured them to leave a few years later.

Even though it's virtually ignored in Mexico, outside of the country it's evolved into a day of BROWN PRIDE.  Which is why it gets huge celebrations in U.S. cities with large Latino populations.