French forces captured Mexico City in 1863 after the Battle of Puebla.
The Mexican victory at Puebla on May 5, 1862, stopped the initial French advance and forced the invaders to retreat. France later sent a larger force and resumed its campaign. After a renewed siege and the fall of Puebla in 1863, French troops advanced to Mexico City.
The occupation allowed Napoleon III to establish a French-backed monarchy headed by Maximilian of Habsburg. Benito Juárez and the republican government continued resistance rather than accepting the imperial arrangement.
Mexico City was the decisive political objective because it was the national capital. Its capture did not mean that Mexico’s resistance had ended; republican forces continued the war, and French support eventually disappeared. The empire collapsed in 1867.