Happy Cinco de Mayo!
In the United States, Cinco de Mayo is treated as a celebration of Mexican heritage, much like St. Patrick's Day is to Irishness or Lunar New Year is to Chinese culture. It's sometimes confused with Mexican Independence Day, which is actually Sept. 16, the day in 1810 when Mexicans first declared their intention to be free from Spanish rule.
Cinco de Mayo is not a Mexican Fourth of July, and it's not "Drinko de Mayo," as the beer companies have tried to fashion it. In fact it celebrates the Battle of Puebla on May 5, 1862, when a ragtag Mexican army fought off an attack by the larger and better-equipped French force sent by Emperor Napoleon III to conquer Mexico.
The French, along with Spanish and English troops, had invaded Mexico in 1861 after Mexican President Benito Juarez declared he was suspending payment on the country's foreign debts. The Spanish and English withdrew after negotiating settlement of the debt. But Napoleon, hoping to gain a foothold in the Americas to counter the growing power of the United States, ordered his troops to attack.
At the Battle of Puebla, in central Mexico, 2,000 Mexican troops successfully defended their forts against 6,000 French soldiers. They won the battle, but Napoleon won the war, installing his cousin Maximilian as emperor of Mexico. It wasn't until 1867 that he was deposed and Juarez regained the presidency.
Though the victory at Puebla was short lived, for Mexicans Cinco de Mayo signifies the pride of a scrappy underdog in fending off the foreign invaders.