The federal response to the emergency in the areas damaged by Hurricane Katrina has been widely condemned as too little, too late.

Three days after landfall, only a handful of National Guard troops had arrived. Those forces were specialized units such as military police companies (to try to restore order), small search-and-rescue units (to seek out individuals trapped in attics), small reconnaissance units (to map the devastation) and small medical units.

It's worth considering what an all-out federal effort would have looked like. A competent federal response would have focused simultaneously on provisioning and evacuation. Above all, a competent response would have been rapid. By Tuesday afternoon the Air Force could have been dropping emergency supplies down to concentrations of survivors. By Wednesday morning, mass evacuation of survivors could have begun. By Thursday night, most of the mass evacuation could have been completed.

The most immediate need was in low-lying areas where people were trapped without adequate food, water and medicine. The best solution was simply to move people from areas located below sea level to temporary shelters. That evacuation would have required numerous rugged vehicles. Thousands of such vehicles were not far away and could have reached New Orleans almost immediately after the disaster struck. Along with the evacuation vehicles, there were fuel trucks, communications systems and security forces readily available. There were even electricity generators and water purifiers ready to be moved to the disaster area.

I estimate that at least 7,500 troops in 1,500 vehicles could have arrived from Fort Hood, Tex., within 72 hours of notification. Had they been alerted on Sunday, substantial lead elements could have arrived in New Orleans by Tuesday evening.

It's a little over 550 miles from Fort Hood to New Orleans. Cars make the trip in 12 hours. An Army convoy would travel more slowly, but would be capable of rapid movement along highways. Call it 24 hours from the time the first battalion convoy moves out of the motor park to when it arrives at the water's edge of the flooded city and starts establishing security and loading survivors.

With two soldiers per vehicle for security and some crowding of the evacuees, this evacuation force would have had a lift capability of something like 10,000 people per trip. Almost all the survivors would have been evacuated, at least to emergency shelters on high ground where food, clean water and basic medical care could have been provided right out of the military vehicles. Those trips could have been completed within 48 hours after the Army arrived.

It would have been a somewhat harrowing evacuation. Army vehicles are not very comfortable. Some evacuees would have ended up riding in the backs of empty ammunition trucks, cargo trucks and other such vehicles. But they would have been removed from the flood waters that were slowly killing them. The Army's more people-friendly vehicles could have been used to transport invalids from hospitals.

Fort Hood was not the only source of vehicles, personnel, food, water, gasoline, electricity, communications, etc. There was also Fort Polk in Louisiana (243 miles away) and Fort Knox in Kentucky (678 miles).

Critics of this scenario will point out that the Army wasn't ready to respond and would have needed time to summon personnel, reconfigure vehicles, load supplies, etc. That merely raises a question: Why wasn't the Army preparing for this on Sunday? Hundreds of thousands of people were already clogging the interstates. Every planning study of a large hurricane striking New Orleans indicated that tens of thousands of residents would be left behind after the exodus of privately owned vehicles. And it was clear by Sunday morning just from the television pictures that a mass evacuation would be needed. The military is the only organization in the United States that has the capacity to transport tens of thousands of people quickly from an area without electricity, telephones and working gas stations.

Why wasn't that done? Why didn't the federal government mount an eminently doable rapid evacuation? It's an important question, because rapid mass evacuation is often the only workable response to large-scale disaster. Rapid mass evacuation is our only practical response to large hurricanes, earthquakes, tsunamis, forest fires, nuclear detonations, space-object impacts, etc.

It's almost certainly only a matter of time before San Francisco or St. Louis has to be evacuated in the aftermath of a devastating earthquake. Maybe next time, thousands of Americans won't be left to die while thousands of usable vehicles sit in motor pools and trained soldiers are nearby.

Louis Hicks is a professor of sociology at St. Mary's College of Maryland, where he specializes in military sociology. He served in military intelligence during the Cold War.

As the federal rescue effort gains momentum on Sept. 1, two residents of flooded New Orleans are winched to safety in a military helicopter.