The Battle of Puebla

France invaded to collect debts and install an emperor. At Puebla, some 4,500 Mexican troops under Ignacio Zaragoza — many of them poorly armed farmers and indigenous militia — held the hills above the city against a French force nearly twice their size and considered the finest army in the world.

The French took Puebla a year later and held Mexico for five, but the date stuck. It is a modest holiday in Mexico and a much larger one among Mexican Americans, who first marked it while the United States was fighting its own civil war.