An army aid convoy headed toward the US border on yesterday was due to become the first Mexican military unit to operate on US soil since 1846. It carried water treatment plants, mobile kitchens and supplies to feed the victims of Hurricane Katrina.
Large Mexican flags were proudly taped to many of the 35 olive-green Mexican Army trucks and tractor trailers as they rumbled northward out of Mexico City on Tuesday morning.
The office of Mexican President Vicente Fox said the convoy was due to cross into Laredo, Texas, early today.
Radio talk shows and newspapers buzzed with excitement at this turning of the tables for Mexico, which has long been on the receiving end of US disaster relief, and which lost half its territory to the US in the 1846-'48 Mexican American War.
"This is the first time that the United States has accepted a military mission from Mexico" for such work, said Javier Ibarrola, a newspaper columnist who writes about military affairs in Mexico. "This is something that's never happened before."
The convoy had "a very high symbolic content," said Javier Oliva, a political scientist at Mexico's National Autonomous University. "This is a very sensitive subject, for historic and political reasons," he said.
The trucks, carrying 195 unarmed soldiers, officers and specialists, are to proceed to Houston, Texas where they will apparently be used to produce water and hot meals for people evacuated from the New Orleans area.
The convoy included two mobile kitchens that can feed 7,000 people each per day, three flatbed trucks carrying mobile water treatment plants, and 15 trailers of bottled water, blankets and applesauce.
It also includes military engineers, doctors and nurses.
Mexico has sent disaster relief aid missions to other Latin American nations, but not to the US.
In their last formal military incursion in 1846, Mexican troops marched just north of the Rio Grande into Texas, which had then recently joined the US.
From Mexico's point of view, the troops did not enter the US even then: at the time, Mexico did not recognize the Rio Grande as the US border.
The two countries quickly became mired in the Mexican-American War, which led to the loss of half of Mexico's territory in 1848.
Mexico sent a squadron of pilots to the US in the 1940s, but they served outside the US -- in the Philippines -- in World War II.
Experts said the only other military incursion by Mexicans came in 1916, when revolutionary leader Pancho Villa led a group of irregular fighters in a brief raid on Columbus, New Mexico, in what is considered the last battle against foreign forces on US soil.
"But this [aid mission] is a military unit temporarily stationed in the US. That's very different from Pancho Villa did in Columbus," said Roderic Ai Camp, a professor at Claremont-McKenna College in California who has studied the Mexican Army.
The convoy was controversial for some Mexican senators, who said Fox should have sought Senate approval for sending the troops.
But the government was already planning another 12-vehicle aid convoy for this week. It has also sent a Mexican navy ship heading toward the Mississippi coast with rescue vehicles and helicopters. The ship Papaloapan left the Gulf coast port of Tampico on Monday and was scheduled to dock yesterday afternoon in the Mississippi River at a spot about 30 miles south of Biloxi, Mississippi.