Veracruz was the Mexican port city occupied by the intervention force before the French advance toward Puebla.
Veracruz is Mexico’s principal historic Gulf port and a natural entry point for European troops arriving by sea. French forces landed there during the intervention that followed Mexico’s suspension of foreign-debt payments.
From Veracruz, the French moved inland toward Mexico City. Their advance led to the Battle of Puebla on May 5, 1862, where Mexican troops stopped the first major push. The route from the coast through Puebla was strategically important because the capital lay farther inland.
Veracruz is sometimes confused with Acapulco, another famous Mexican port, but Acapulco is on the Pacific coast. The French intervention associated with Cinco de Mayo began on the Gulf side, making Veracruz the relevant port.