At the National Museum of Antiquities, where priceless artifacts had been wrapped in foam and secured in windowless storage rooms to protect them against U.S. bombs, an army of looters perpetrated what war did not: They smashed hundreds of irreplaceable treasures, including Sumerian clay pots, Assyrian marble carvings, Babylonian statues and a massive stone tablet with intricate cuneiform writing.

As employees returned today to survey the damage at one of the world's greatest repositories of artifacts, they encountered devastation that defied their worst expectations. The floor was covered with shards of broken pottery. An extensive card catalog of every item the museum owns, some of which date back 5,000 years, was destroyed. A cavernous storeroom housing thousands of unclassified pieces was ransacked so badly that an archaeologist predicted it would be impossible to repair many of the items.

"Our heritage is finished," lamented Nabhal Amin, the museum's deputy director, as she surveyed a Sumerian tablet that had been cracked in two. "Why did they do this? Why? Why?"

As throngs of angry and impoverished Iraqis sack government offices and private businesses, making away with everything from porcelain bathtubs and police uniforms to forklifts and ambulances, it has become increasingly clear that the looting that was sparked by the fall of Saddam Hussein's government -- largely unchecked by U.S. forces -- has wreaked more damage on Iraq's civilian infrastructure and economy than three weeks of U.S. bombing.

The damage could have a significant effect on the Bush administration's military and political goals in Iraq, complicating efforts to win the trust of ordinary people, return cities to normalcy and eventually reconstruct the country. Many here feel U.S. forces in the city -- Army units on the western side of the Tigris River and Marines on the eastern side -- could and should be doing more to crack down on looting. As the mayhem continues, they have begun shifting blame for the lawlessness from their fellow countrymen to U.S. troops.

"If there were five American soldiers at the door, everything would have been fine," Amin said about the museum. "They're supposed to be here to protect us. They should be protecting us."

U.S. bombardment largely targeted centers of Hussein's power -- his palaces, intelligence offices and military installations. But the thievery that has enveloped the capital and other cities across the country, from Mosul in the north to Basra in the south, has resulted in broader, more indiscriminate destruction. Although television images of the lawlessness have focused on people carting chairs and desks from government offices and ornate fixtures from Hussein's many palaces, visits inside several government buildings suggest the pillaging is more profound.

At the Foreign Ministry, for instance, looters have stolen every single piece of furniture. They have taken away thousands of files, leaving only scattered papers on the floor. At the Yarmouk Hospital, the largest medical center on the western side of Baghdad, they took not just all the beds, medicines and operating room equipment, but also the CAT, MRI and ultrasound scanners. And along Rashid Street, one of the capital's main shopping avenues, some merchants said they have lost so much merchandise that they cannot afford to reopen their shops.

"The bombing was terrible for sure, but it is not ruining our city like these looters are," growled Sherko Jaf, a dentist, as he watched a band of young men hauling rolls of carpet out of the 10-story Foreign Ministry building and placing them inside a yellow dump truck. "How will this ministry ever work again? You know, even if we don't have Saddam Hussein, we will still need a foreign ministry."

U.S. military commanders contend they are doing as much as they can to stem the thievery. But they acknowledge they do not have enough troops to patrol every looting-prone part of the city while also focusing on stamping out lingering pockets of resistance and guarding against suicide attacks.

Some Iraqis, however, question the allocation of U.S. forces around the capital. They note a whole company of Marines, along with at least a half-dozen amphibious assault vehicles, has been assigned to guard the Oil Ministry, while many other ministries -- including trade, information, planning, health and education -- remain unprotected.

"Why just the oil ministry?" Jaf asked. "Is it because they just want our oil?"

U.S. military officials said the Marines have been guarding other sensitive installations, including the Interior Ministry and the Irrigation Ministry, and have stepped up patrols of commonly looted areas, dispatching troops in small convoys of Humvees to deter and apprehend thieves. But during a lengthy drive though the capital today, such patrols could only be seen in two wealthy neighborhoods.

In one of those areas, the Arresat district, a boy on a bicycle flagged down a Marine unit after noticing four men trying to enter a photography shop. The Marines arrived, brandished their M-16 rifles and ordered the men to lay face down on the sidewalk.

As a crowd gathered around, the men insisted they were entering the shop at the owner's request to remove merchandise before looters got to it. Their keys did open the front door. But Marine Gunnery Sgt. Mark Grice, 31, was unconvinced. He noticed a hammer and anvil near the door, and he pointed out that the men's truck had no license plates.

As the men started arguing with some of the Marines, Grice sighed. "Three days ago, we were mortar men," he said. "Now we're babysitters."

Finally, he compromised. The men would have to put the merchandise back in the shop, lock the keys inside and promise never to be seen by Grice again. Grice wondered aloud whether he was making the right call. He figured one of the men was an employee of the shop but that the removal of the goods was unauthorized. By letting them go, he mused, would they just hit another shop?

"How are you supposed to transition from being a warrior to King Solomon?" he said.

A few miles away, near the Interior Ministry, throngs of eager young men were hauling desk chairs and other office equipment less than a block away from a Marine camp.

Privately, some U.S. officials involved in reconstruction have expressed concern that failure to quickly crack down on looting could have worrisome, long-term consequences for the transitional government that the Bush administration wants to set up here. "By not being more aggressive now, there is the risk of bigger problems later," one official said.

Some military officers believe some of the gun battles that have recently erupted among different groups of Iraqis may be turf wars over places to loot or an escalation of long-standing conflicts in the new lawless environment.

"Once the Americans allowed this, it was 'Game On,' " said Lt. Erik Balascik of the Army's 3rd Infantry Division.

Many Iraqis and some of the few Western aid workers in the capital expressed wonder that the U.S. military was not more prepared to handle civil disturbances stemming from Hussein's downfall and evaporation of his once-pervasive security forces. "It was predicted," said Roland Huguenin-Benjamin, a spokesman for the International Committee of the Red Cross. "Everyone knew it was coming."

The lack of police on the streets -- except for young boys in looted police uniforms -- has prompted some neighborhoods to organize block patrols, complete with men armed with AK-47 assault rifles. After a prominent Shiite Muslim cleric issued an edict calling on people to stop looting, some mosques also have set up anti-looting militias whose members man roadblocks and confiscate items deemed to have been pilfered.

At the East Karrada Mosque today, one room was full of chairs, electronics and files from a nearby U.N. Children's Fund office that had been looted, but then secured by the mosque militia, which promised to track down the rightful owners. Among the men at the mosque, there was near universal agreement that U.S. soldiers could put an end to the plunder if they wanted to.

"I tell the United States, 'You wanted to overthrow the government so you should have taken responsibility and put one soldier in front of every government building,' " said Saad Tuema, a portly, middle-aged engineer who claimed not to have slept in three days because he has been hunting looters. "Instead, they just stood by and let it happen."

That is a common perception here. Some attribute the lack of an aggressive U.S. response to a miscalculation. Others ascribe it to underhanded motives.

"They wanted to let these robberies happen so the Iraqi people will be bankrupt and they will need American assistance," said Mehdi Zuemi, a clerk in the Foreign Ministry who observed his office being destroyed today. "They'll use our oil to pay for it."

At the Yarmouk Hospital, which was hit by a U.S. tank shell during a street battle Wednesday, doctors said they have no interest in getting protection from U.S. troops. "We just want them to leave us alone," said Amir Kadhim, a general surgeon. "We don't need their protection. We'll do it ourselves."

But a promised contingent of armed guards from the surrounding Karkh neighborhood has not yet materialized. Until they arrive, Kadhim said, the doctors are too nervous to work in the building, so they perform minor surgery, without the benefit of anesthetics or sterilized equipment, on the hospital's portico.

"Yesterday, the looters came with knives and stole our only working ambulance," he said. "How can we feel safe here?"

At the National Museum of Antiquities, Amin said she wants American soldiers -- and lots of them. Today, as she led a small group of journalists through the museum, five looters armed with an ax sneaked into one of the rooms, prompting several of the journalists to give chase. "They will keep coming here until there is nothing left to take," she said.

For the past 70 years, the museum has served as the showcase for records and collections of art and artifacts from the beginnings of ancient Sumer in 3,500 B.C. to the end of Islam's Abbasid Caliphate in 1258 A.D. "There are thousands of one-of-a-kind objects," said John Russell, an archaeologist and art historian at the Massachusetts College of Art. "This material is absolutely irreplaceable."

Many of the museum's most valuable pieces had been moved to another location before the war, but items that were too big, such as marble statues and reliefs, were left in place and covered with foam and lined with sandbags.

"We were ready for the bombs," Amin said. "Not the looters."

As she quickly walked through more than three dozen rooms, Amin did not catalog what was missing or damaged. There was just too much. But every few minutes, she would stop in front of an empty pedestal or a decapitated statue.

"This was priceless," she sobbed as she pointed to two seated marble deities from the temple at Harta that had been defaced with a hammer. Later, after observing more damage, she broke down again. "It feels like all my family has died," she wept.

Even storage rooms and workshops were trashed. An old Babylonian wooden harp was broken in two and its gold inlay scraped off. But most inexplicable to her was the destruction of rooms that contained no artifacts, just archaeological records and photographs.

"I cannot understand this," she said. "This was crazy. This was our history. Our glorious history. Why should we destroy it?"

Staff writers Mary Beth Sheridan in Baghdad and Guy Gugliotta in Washington contributed to this report.

A museum worker sits in shock at the National Museum of Antiquities, where bombing was expected to pose the greatest threat.Nabhal Amin, museum deputy director, broke down as she surveyed the destruction.Deputy Director Nabhal Amin and her husband walk through the Baghdad museum. "If there were five American soldiers at the door, everything would have been fine," Amin said.An employee sits atop remnants of the collection. Many of the most valuable pieces had been moved to another location before the war, but items that were too big were covered with foam and lined with sandbags.