France captured Puebla in 1863 after its earlier defeat at the Battle of Puebla in 1862.
The Mexican victory on May 5, 1862, delayed the French advance but did not end the intervention. France responded by sending a larger force under Élie-Frédéric Forey. That army returned to Puebla and began a prolonged siege in March 1863.
Mexican defenders resisted for weeks, but supplies eventually ran out. Puebla fell in May 1863, opening the road to Mexico City. French forces captured the capital soon afterward and helped establish the Second Mexican Empire under Maximilian.
The contrast between the two years is important. Cinco de Mayo celebrates the Mexican victory of 1862, while the fall of Puebla in 1863 shows that the earlier success was a delay rather than a complete military victory.