In September 2005, units of the Mexican Armed Forces responded to the emergency situations after Hurricane Katrina with aid and assistance, appearing as a flagged, uniformed force in the United States for the first time since World War II in the 1940s and the first operational deployment of Mexican troops to the U.S. in 159 years.

The Mexican Armed Forces are the military forces of the United Mexican States. The Spanish crown established a standing military in colonial Mexico in the eighteenth century. After Mexican independence in 1821, the military played an important political role, with army generals serving as heads of state. Following the collapse of the Federal Army during the 1910–1920 Mexican Revolution, former revolutionary generals systematically downsized the size and power of the military. The Mexican military forces are composed of two independent entities: the Mexican Army and the Mexican Navy. The Mexican Army includes the Mexican Air Force, while the Mexican Navy includes the Naval Infantry Force and the Naval Aviation (FAN). The Army and Navy are controlled by two separate government departments, the National Defense Secretariat and the Naval Secretariat, and maintain two independent chains of command, with no joint command except the President of Mexico.