The holiday celebrates a surprise victory by a smaller Mexican force over the French army.

In 1862, France invaded Mexico. The French army was huge, highly trained, and considered one of the best in the world. When they marched on the city of Puebla, they expected an easy win. Instead, a smaller Mexican force led by General Ignacio Zaragoza fought back and won. It was a huge boost of confidence for Mexico, even though France eventually took over the capital city a year later.