BASRA, Iraq - Adel Abdul Imam al-Helfi sat on the floor of his dim 12-by-18-foot hovel in a dangerous district in downtown Basra, trying to explain what it was like to live in a kind of enclave that has sprouted up all over the country since the invasion two years ago.
Mr. Imam, once a resident of a remote rural swamp, rushed here with hundreds of his tribal kin after Saddam Hussein's government fell, searching for opportunity and jobs. Instead, he said quietly, they found a place worse than any he had ever known. His fellow tribesman Radi Taqi al-Helfi called up an expression used for someone with a terminal illness, "We are semi-dead."
The great dislocations unleashed by the invasion have created poor, dangerous and often ethnically homogenous urban enclaves on a scale not seen here before. Other areas, like parts of Baghdad's central Baab Sharqi district, had been impoverished before the invasion after years of sanctions, but it became infested with serious crime only after Mr. Hussein's police state collapsed and was replaced by weak security or none at all.
Before the invasion, said Col. Faisel Ali, an investigator in a Baghdad major crimes unit, criminals feared the heavy police presence in Baab Sharqi. "Now, I'm afraid to go to Baab Sharqi, because if the criminals know I'm there, they will kidnap or kill me," Colonel Faisel said.
Mr. Hussein also worked to destroy any sense of community among out-of-favor groups, and failing all else, simply denied that such enclaves existed. As a result, the notion of what an American might call a ghetto is novel enough here that Iraqis do not have a proper word for it.
Even now, with consummately Iraqi ridicule, people in the most common enclaves for the new poor - government complexes that were looted, abandoned and then filled with squatters after the 2003 invasion - are called Hawassim, literally "those who produced the decisive victory," or just "the Decisives." The reference is to Mr. Hussein's melodramatic term for the invasion: Maarekat al Hawassim, or the Decisive Battle.
Members of Mr. Imam's tribe, whose accents, ragged dress and weathered, swarthy faces stand out on the streets of Basra, were first driven by war, drought and bad luck into exile in places like Iran and Saudi Arabia.
Since 2003, they have returned to the Iraqi south and have gathered in the crumbling and sewage-fouled remains of a former naval compound in the middle of Basra. It is a world all its own.
Unlike the great majority of people here, Mr. Imam's family did not vote in the recent elections, because, he said, they were confused about whether they had the proper identification cards and about where to cast ballots in their neighborhood.
Mr. Imam's 8-year-old son has been denied entry to school - he was told that there was no room; his severely diabetic mother has not received proper medical treatment; and there is barely enough electricity in his family's tiny room for a single overhead bulb.
"And whenever you go to the officials and say, 'Please help us,' they say, 'Don't speak, because you are staying in unofficial places,' " said his brother, Jassim Abid Ali al-Helfi.
The last time anything approaching this phenomenon took place in Iraq was in the years surrounding the July 14, 1958, coup that overthrew the monarchy, said Ghassen Atiyyah, a former educator who is the director of the Iraq Foundation for Development and Democracy, based in Baghdad.
As the poor from all over the Iraqi countryside created a shantytown on Baghdad's northeastern outskirts, Abdul Karim Qasim, who was prime minister from 1958 to 1963, built new housing there and called the district Revolution City. Mr. Hussein renamed it Saddam City. After the 2003 invasion, the district - now dominated by religious Shiites - became Sadr City, after a revered cleric who was killed during Mr. Hussein's rule.
Although the district had always remained a kind of slum that many Baghdadis avoided after dark, Sadr City became a much more lawless place after the invasion, Dr. Atiyyah said. But it was not the only Baghdad neighborhood that went into decline.
Within Baab Sharqi (literally East Gate, although it is in the center of the city), the Bataween and Orfaliya districts have become havens for illicit drug and alcohol sales, where crime and prostitution flourish just off central commercial streets. Orfaliya is heavily populated by Sudanese who immigrated as guest workers during Mr. Hussein's rule.
Bataween, dotted with once elegant homes, was a neighborhood of well-to-do Jewish families that were numerous in Iraq decades ago. Drawing on their heritage from ancient Babylon and treated well in the Ottoman Empire, Iraqi Jews made up as much as 30 percent of Baghdad's population in the 1920's and were never forced to form poor enclaves, Dr. Atiyyah said.
But with the strife that accompanied the creation of Israel in 1948, the Jews began moving out. Bataween later became a Christian neighborhood and has most recently attracted poor Muslims in a historical progression that links it to a classic American ghetto. (The word, pronounced here as jetto, sometimes surfaces in Iraq, but it is not commonly used.)
Most of the recent changes are direct functions of the chaos that has reigned in Iraq since the invasion, Dr. Atiyyah said.
"Who is paying attention to social and economic development?" Dr. Atiyyah said. "The government is busy with other things."
To government officials in Basra, the districts have already become synonymous with crime, hopelessness and strange customs. The former marsh people routinely raise water buffalo and thatch reeds for resale in their urban dwellings, just as they did in the swamp.
"They brought their habits to the city, and people living in the city are having real problems with them," said Abdula H. Neshan, an official in the Basra governor's building.
There is disagreement about those assertions inside the old naval compound, where the rows of partly smashed barracks, officers quarters and recently built reed huts cover perhaps half a square mile.
Other families live in a former brig - the bars are still on the windows - surrounded by a moat of greenish sewage. Men with AK-47's wander the grounds among chest-high piles of scrap iron and rotting garbage.
"There is some sort of misunderstanding," said Sheik Muhammad Faddal Seeyah Hussein al-Amarra, the leader of a large slice of the compound. "Everywhere in Basra there are such problems."
Sheik Muhammad is the slum's sharpest dresser, decked out in a fine head cloth and gold-embroidered dishdasha, which is draped regally over a Western-style pinstriped jacket. He estimated that in his part of the compound alone there were 150 families. Since the invasion, his tribe - hunters, fishermen and fighters back in the swamp - have repeatedly sought jobs in the Basra police force and the Iraqi Army while doing odd jobs on construction sites.
A tiny old woman dressed in a black abaya, Zenuba Hanoon Muail al-Helfi, explained succinctly what had become of those efforts, "No one is employed."
Mr. Imam, 32, and his family of seven live on government food rations and the $3 to $4 he makes every week or 10 days as a temporary construction worker. In a society whose bedrock concept is the alpha male, Mr. Imam sleeps late most days and helps take care of his children around the compound.
"If I stay in the same routine," Mr. Imam said with shame in his voice, "I will suffer from mental disease."