Hurricane Katrina relief
In September 2005 Mexican army convoys traveled to the U.S. to help in the Hurricane Katrina relief effort.

Mexican army convoys and a navy ship laden with food, supplies and specialists traveled to the United States including military specialists, doctors, nurses and engineers carrying water treatment plants, mobile kitchens, food and blankets.

The convoy represents the first Mexican military unit to operate on U.S. soil since 1846, when Mexican troops briefly marched into Texas, which had separated from Mexico and joined the United States. There were complaints from Mexican senators because President Vicente Fox did not ask for congressional permission to send troops overseas, as required by law, but the complaints were dismissed because it was a humanitarian mission and no armed forces were involved, but only unarmed military personnel (medical, engineers, etc.).