WASHINGTON, Sept. 1 - When Michael D. Brown, director of the Federal Emergency Management Agency, returned in January from a tour of the tsunami devastation in Asia, he urgently gathered his aides to prepare for a similar catastrophe at home.
"New Orleans was the No. 1 disaster we were talking about," recalled Eric L. Tolbert, then a top FEMA official. "We were obsessed with New Orleans because of the risk."
Disaster officials, who had drawn up dozens of plans and conducted preparedness drills for years, had long known that the low-lying city was especially vulnerable. But despite all the warnings, Hurricane Katrina overwhelmed the very government agencies that had rehearsed for such a calamity. On Thursday, as the flooded city descended into near-anarchy, frantic local officials blasted the federal and state emergency response as woefully sluggish and confused.
"We're in our fifth day and adequate help to quell the situation has not arrived yet," said Edwin P. Compass III, the New Orleans police superintendent.
The response will be dissected for years. But on Thursday, disaster experts and frustrated officials said a crucial shortcoming may have been the failure to predict that the levees keeping Lake Pontchartrain out of the city would be breached, not just overflow.
They also said that evacuation measures were inadequate, leaving far too many city residents behind to suffer severe hardships and, in some cases, join marauding gangs.
Large numbers of National Guard troops should have been deployed on flooded streets early in the disaster to keep order, the critics said. And some questioned whether the federal government's intense focus on terrorism had distracted from planning practical steps to cope with a major natural disaster.
Disaster experts acknowledged that the impact of Hurricane Katrina posed unprecedented difficulties. "There are amazing challenges and obstacles," said Joe Becker, the top disaster response official at the American Red Cross.
Under the circumstances, Mr. Becker said, the government response "has been nothing short of heroic."
But he added that the first, life-saving phase of hurricane response, which usually lasts a matter of hours, in this case was stretching over days.
While some in New Orleans fault FEMA - Terry Ebbert, homeland security director for New Orleans, called it a "hamstrung" bureaucracy - others say any blame should be more widely spread. Local, state and federal officials, for example, have cooperated on disaster planning. In 2000, they studied the impact of a fictional "Hurricane Zebra"; last year they drilled with "Hurricane Pam."
Neither exercise expected the levees to fail. In an interview Thursday on "Good Morning America," President Bush said, "I don't think anyone anticipated the breach of the levees." He added, "Now we're having to deal with it, and will."
Some lapses may have occurred because of budget cuts. For example, Mr. Tolbert, the former FEMA official, said that "funding dried up" for follow-up to the 2004 Hurricane Pam exercise, cutting off work on plans to shelter thousands of survivors.
Brian Wolshon, an engineering professor at Louisiana State University who served as a consultant on the state's evacuation plan, said little attention was paid to moving out New Orleans's "low-mobility" population - the elderly, the infirm and the poor without cars or other means of fleeing the city, about 100,000 people.
At disaster planning meetings, he said, "the answer was often silence."
Inevitably, the involvement of dozens of agencies complicated the response. FEMA and its parent agency, the Department of Homeland Security, were in charge of coordinating 14 federal agencies with state and local authorities. But Mayor C. Ray Nagin of New Orleans complained Wednesday on CNN that there were too many cooks involved.
Unlike a terrorist attack or an earthquake, Hurricane Katrina gave considerable notice of its arrival. It was on Thursday, Aug. 25, that a tropical storm that had formed in the Bahamas reached hurricane strength and got its name.
The same day, Katrina made landfall in Florida, dumping up to 18 inches of rain. It then moved slowly out over the warm waters of the Gulf of Mexico, growing by the hour.
Though its path remained uncertain, the Gulf Coast was clearly threatened, with New Orleans a possible target. Officials from the Pentagon, the National Guard, the Army Corps of Engineers, FEMA and the Homeland Security Department said they were taking steps to prepare for the hurricane's arrival.
Army Corps personnel, in charge of maintaining the levees in New Orleans, started to secure the locks, floodgates and other equipment, said Greg Breerwood, deputy district engineer for project management at the Army Corps of Engineers.
"We knew if it was going to be a Category 5, some levees and some flood walls would be overtopped," he said. "We never did think they would actually be breached." The uncertainty of the storm's course affected Pentagon planning.
"We did not have precision on where it would make landfall," said Lt. Gen. H. Steven Blum, the head of the National Guard Bureau. "It could have been anywhere from Texas all the way over to Florida."
Some 10,000 National Guard troops were mobilized, 7,000 of them in Louisiana and Mississippi. But the Defense Department could not put soldiers and equipment directly in the possible path of the storm, General Blum said.
On Saturday, at the urging of FEMA, Mr. Bush declared an emergency in Louisiana, allowing the agency to promise financial assistance to state and local governments and to move ready-to-eat meals, medicine, ice, tarpaulins, water and other supplies to the region.
By Sunday, Katrina had become a Category 5 hurricane, with winds of 175 miles per hour. The president extended the emergency declaration to Mississippi and Alabama. Mayor Nagin, who had urged New Orleans residents to flee on Saturday, ordered a mandatory evacuation.
It would have been up to local officials, a FEMA spokeswoman said, to hire buses to move people without transportation out of the city.
Rodney Braxton, the chief lobbyist for New Orleans, said many of the city's poorest "had nowhere to go outside the region and no way to get there." He added: "And there wasn't enough police power to go to each house to say, 'You have to go, come with me.' "
In a city with so many residents living in poverty, the hurricane came at the worst possible time: the end of the month, when those depending on public assistance are waiting for their next checks to be mailed on the first of the month. Without the checks, many residents didn't have money for gasoline, bus fare or lodging.
City officials said they provided free transportation from pick-up points publicized on television, radio and by people shouting through megaphones on the streets. In addition to the Superdome, officials opened schools and the convention center as shelters.
Mr. Braxton said he believed the city was "aggressive enough" in conducting the evacuation. "We had everything we thought we needed in place," he said. "I don't think anybody could ever plan for the magnitude that Katrina ended up being."
But Susan Cutter, a geography professor at the University of South Carolina and an emergency preparedness expert, said Mayor Nagin should have ordered a mandatory evacuation on Thursday or Friday.
"Evacuation is a precaution," she said. "I don't think they would have taken a political hit if they had ordered it, and it helped."
While New Orleans residents fled the city or gathered in the Superdome, federal agencies positioned search and rescue teams and medical assistance teams from Tennessee to Texas, according to Michael Chertoff, secretary of homeland security.
Before it made landfall on Monday, the storm turned slightly to the east, avoiding a direct hit on New Orleans. The winds had eased slightly to 140 miles per hour, reducing Katrina's strength to Category 4, and officials counted themselves lucky.
But on Tuesday, when the levees breached, a desperate situation became catastrophic. There was no fast way to fix them, Mr. Breerwood of the Army Corps said, because delivery of heavy-duty equipment was hindered by the destruction.
The National Guard was having similar troubles. While troops were stationed in the region, they could not move quickly into the New Orleans area. And in Mississippi, the zone of destruction was so widespread, it was difficult to cover it all quickly, officials said.
"It is not a function of more people, but how many people can you move on the road system that exists now in Louisiana and in Mississippi," said General Blum of the National Guard. "How many people can you put through that funnel that a storm has taken four lane highways and turned them into goat trails?"
On Wednesday, Mr. Bush, having cut short his vacation, convened a federal task force. With looting spreading throughout New Orleans, Guard officials said they were doubling the call by this weekend, to 21,000 forces, one-third of them military police officers. On Thursday, General Blum said more than 32,000 Guard members would be deployed in the gulf region by Monday.
Currently, the states' governors control their National Guard, with the Pentagon and other federal agencies like FEMA, coordinating operations with the state. The administration has resisted federalizing the relief operation, in large part because officials say it would severely limit the National Guard's ability to conduct law enforcement missions for which they are specifically trained.
"Federalizing the National Guard for purposes of law enforcement would be a last resort, not a first resort," said Paul McHale, assistant secretary of defense for homeland security, told reporters on Thursday.
A 1878 law restricts active-duty military forces from performing domestic law enforcement duties. But in extreme emergencies, like some of the race riots and civil disorders in the 1960's, federal troops have been sent in to restore order.
The administration has also balked at ordering active-duty military forces, such as the 82nd Airborne Division from Fort Bragg, N.C., to intervene in a civilian law enforcement role to stop looting and restore order. Late Tuesday, the Pentagon dispatched five ships to the gulf, but four of the ships are coming from Norfolk, Va., four days' sailing time away.
Some military analysts criticized the Pentagon's response.
"Is the problem that they are only just now beginning to understand how serious the damage was?" said John Pike, director of GlobalSecurity .org, a national security policy group in Washington. "Did they not have a contingency for a disaster of this magnitude?"
The chaotic response came despite repeated efforts over many years to plan a coordinated defense if the worst should occur. As recently as July 2004, federal, state and local officials cooperated on the Hurricane Pam drill, which predicted 10 to 15 feet of water in parts of the city and the evacuation of one million people.
Martha Madden, who was the Louisiana secretary of environmental quality from 1987-1988, said that the potential for disaster was always obvious and that "FEMA has known this for 20 years."
"Hundreds and hundreds of thousands of dollars were spent, in studies, training and contingency plans, scenarios, all of that," said Ms. Madden, now a consultant in strategic planning.
The Army Corps, she said, should have had arrangements in place with contractors who had emergency supplies at hand, like sandbags or concrete barriers, the way that environmental planners have contracts to handle oil spills.
While his agency is facing harsh criticism, Patrick Rhode, FEMA's deputy director, defended its performance as "probably one of the most efficient and effective responses in the country's history."
He recalled that after Mr. Brown, his boss, returned from his tsunami tour, he asked if the United States was better prepared for a disaster than the ravaged countries he had visited. "We felt relatively comfortable that this country could mobilize the response necessary," he said.