What happened a year after this battle?

The French returned and conquered the Mexicans is the correct answer to this question. Though this occurred a year later, it doesn't stop Mexico from celebrating their victory in 1862. Still today, this victory is celebrated through a holiday called Cinco de Mayo.

The thanks for celebrating this day goes to then-President Juarez. On September 16, 1862, he declared May 5 a holiday in honor of the victory that occurred that day. Cinco de Mayo is not just a Mexican holiday, but it is celebrated all over the world with parades, ceremonies, costumes, alcoholic drinks, and good Mexican food.