This is a quick history lesson for my friends who don’t live in areas with high Mexican populations, and numerous Taco Bells don’t count. What is Cinco de Mayo exactly? Contrary to its popularity and title looking like the Fourth of July in English, it isn’t Mexican Independence Day, that’s in September.
Back in 1862 the French invaded Mexico to put their guy Maximilian in charge, but that’s another story. The US couldn’t do anything about it since we were pre-occupied with American-upon-American violence during the Civil War. So French forces arrived and made their way to take over in Mexico City unopposed until May 5 (1862). Somewhere along the way, the invading army was defeated in battle by a ragtag group of Mexican forces (translation, peasants conscripted into fighting). This didn’t really make much difference afterwards as it proved to be only a setback for the French; Mexico was still defeated later and the French ruled the country through a puppet until 1868.
This victory is celebrated because it was (and still is) their only victory against a foreign army.