On the night before Baghdad's fall, Hussein, a Baath Party militiaman, saw the omens of a gathering disaster.

Soon after midnight, he said, the five commanders of his unit went home unexpectedly. They said they were leaving to have dinner. Three hours later, Hussein and his 80 youthful fighters came under attack. They were hit not by U.S. forces but by neighbors who were worried the fighters had invited U.S. bombing by stashing grenades, light artillery and rocket-propelled grenades in their base at the Future Girls' School in Sayidiya.

The firefight lasted 30 minutes -- complete with a rocket-propelled grenade fired by the militia into a house.

"It came from the sky and then it came from the people," said Hussein, a vocational student, his face still tinged with fear in recounting the early hours of Wednesday morning when the Baath Party fighters were besieged. "We couldn't get out. We were surrounded."

In groups of two, they fled by car and on foot to another Baath Party office in the nearby neighborhood of Saddam. They were tired, terrified and hungry, having lived on potatoes for days. On the city's outskirts loomed the frightening firepower of U.S. forces preparing to storm the city. Their leadership was gone, their morale was sapped, and they plotted their next move.

"We talked among ourselves," said Hussein, looking older than his 23 years and reluctant to give his last name for fear of retribution from a city with vengeance on its mind. "We made a decision, and everyone decided to go home. We all took off."

Hussein's account casts light on Baghdad's decisive moment, when thousands of loyalists of President Saddam Hussein simply faded away and his government -- once so feared and powerful -- just vanished.

From dusk to dawn, Baghdad's defenses virtually disintegrated. Thousands of Baath Party militiamen, who had manned every street corner, bridge and intersection, changed into street clothes and went home. Saddam's Fedayeen, black-clad militiamen, who had vowed to fight to the death, were gone by morning, some of them leaving their weapons behind. The remnants of the Republican Guard, the vaunted pillar of the regime's defense, played so small a role that Baghdad fell far more easily than the restive cities of the south.

In the days since, Baghdad residents have asked the question: Why did their city collapse with barely a fight?

Senior Baath officials insist orders were given to disband, and residents confirm that the departure of higher-level officials seemed systematic and deliberate. But the circumstances of that order -- in particular, who gave it -- remain a mystery.

"There is something dubious, something unclear, something unexplainable about what happened that night," said Wamid Nadhme, a professor of political science at Baghdad University and a rare voice of criticism of the government under Hussein's rule.

As in so many times of tumult, the unknown has given rise to rumors spoken with the authority of truth. Many of them revolve around the puzzle of what happened to all the country's senior officials, not one of them known to be captured. Their departure seemed as striking as it was hasty. Only Information Minister Mohammed Saeed Sahhaf was seen in the days before Baghdad's fall. In the unfinished house of Ali Hassan Majeed, Hussein's cousin and one of the government's most feared and despised officials, looters stumbled across the discarded Iraqi identification card of his wife Shima and citizenship papers of his daughter Hiba and son Abdulla.

In fevered gossip, many have insisted that Hussein dispatched his family to Damascus in two or three buses two weeks before the war's end. Others speculate that he and others went north to Mosul or Tikrit or sought refuge with tribes on whom the government had showered patronage -- cars, guns and money -- since the end of the 1991 Gulf War.

For many, the government's fall was inevitable. Its 35 years of absolute power engendered such loathing that no one was willing to defend it, a disintegration akin to the abrupt collapse of totalitarian regimes in the Soviet Union and Eastern Europe.

But others voice shame at how Iraq's army -- still a source of pride to some amid the government's tyranny -- failed to defend Iraq.

"After the provinces lasted 20 days, I expected Baghdad to resist four months," said Adel Kamel, a goldsmith in the neighborhood of Bayaa. "Nobody expected Baghdad to collapse in two days. Where's the Republican Guard, where's the army, where's the government, where are the people from Tikrit? He should have given up from the beginning, he should have resigned and respected the people."

"Everyone wonders where they went," said Abu Omar, sitting in a minibus in central Baghdad.

As he spoke, looters systematically dismantled the Ministry of Higher Education. Black smoke poured out of the building, and flames danced over the nearby Ministry of Industry. Young boys wheeled out carts stacked with wood drawers and copiers, and women in black chadors hauled away office chairs. Records from offices were scattered across the street.

"Is this the liberation of our country?" he asked.

One senior Baath Party official said he was told by his supervisor to leave his post on Tuesday and return to his home. The reason given was that the party's militia rifles and rocket-propelled grenades were no match for the might of American forces.

Other residents report that the word went out soon after dusk, as policemen joined the party militiamen in abandoning their posts.

Naseer Hassan, a manager at the international airport, said he was approached by a police car at an intersection along Palestine Street at 6:30 p.m. The blue-uniformed policemen said the city was no longer safe.

"Be careful tonight, we're going to leave the streets," the 46-year-old Hassan recalled one of the officers saying. "The Americans are very close. If we stay here we have two choices -- either they kill us or they take us prisoner."

In his neighborhood of Zayuna, along his street there were five stations of the Baath Party, 10 militiamen in each, who had patrolled the city night and day after the war's start. When Hassan woke up, "they were all gone."

"They were frightened," he said, sitting in the walled garden of his house Friday. "These people are not trained to face tanks or a real army. They know how to use a gun, but not like a professional soldier."

That was the sentiment of Hussein, the militiaman in the neighborhood of Sayidiya. In a conversation in his neighborhood, where he stayed behind doors to dodge neighbors' wrath, he recounted the monotony of service in the militia and the collapse of its defense.

From the war's start, he had the graveyard shift, standing outside the party's base at the Future Girls' School with a Kalashnikov assault rifle from midnight to 4 a.m. The rest of the day, he said, "I just sat." With just a year in the party, he did not receive one of the stipends, ranging from $20 to $100 a month, given to more senior members. He and others relied on food from home. They had little water and less sleep.

Like others, he never bargained for a fight with an army. At one point, when the Americans first entered the city, he said the senior party leaders threatened him and others with a gun to make sure they would fight. But it was the leadership's desertion on the morning of the city's fall that ended any pretense of defending Baghdad in what virtually everyone considered a doomed fight.

"We saw that they were hiding," he said.

But he's ashamed of Baghdad's defeat -- which he calls "a pity." He worries about vendettas that could be waged against the legions of people associated with the government, and he has stayed far from the base and the people who fired on it Wednesday morning. Since the city's fall, he insists, he hasn't slept at all.

As for his future, Hussein said simply, "It's up to the mercy of God."

U. S. troops, guided by Iraqis, search a flooded basement at the headquarters of Iraqi Intelligence in Baghdad. Civilians had reported that prisoners were still being held in an underground prison, but none were found.