Ask residents of Baghdad's Sadr City slum about the probable aftermath of more than 200 killed last week – the largest toll from a single attack since Saddam Hussein's fall – and they speak in apocalyptic terms.
These Shiites fear that the burgeoning instinct for revenge against Sunnis will override calls for calm from clerics and politicians, and deepen the sectarian bloodletting that has defined Iraq in 2006.
If last Thursday's attack proves to be another landmark event that drives Iraq further into civil war, it will complicate even more the American military exit strategy.
"We can compare it to the Hiroshima bomb," says a Sadr City water-department chief, who gave only his nickname, Abu Khadhim. Appeals from anti-US cleric Moqtada al-Sadr, coupled with a three-day lockdown in Baghdad, have checked violence so far.
Expectations of more heavy attacks Monday as the curfew lifted turned to tentative relief when few incidents were reported. These included gunmen shooting on a busy street, killing six.
"Without Moqtada's statement, the [2.5 million] people in Sadr City would go [and] destroy all Sunni neighborhoods," says Abu Khadhim. "If [Shiite clerics] declared war, like [Sunni cleric] Harith al-Dari, then there would be no more Sunnis left in Baghdad. All would be thrown into the Tigris River."
Shiites here say Thursday's car bombs will resonate more than the Feb. 22 destruction of Askariya shrine in Samarra, north of Baghdad, which ignited Shiite revenge attacks and Sunni counterstrikes.
Thousands of civilians have since died as militias, death squads, and insurgents of the majority Shiite and minority Sunni communities began separating themselves. But while there were no casualties when the shrine was blown up at dawn nine months ago, last week's attack has left Sadr City choked with mourning tents and tearful survivors.
"I can't measure the anger of the man whose mother or sister or children are killed," says Ali Abdullah, a Sadr City shop owner. "My heart wants to explode, and other people's, too, because we are very sad, and very angry about what has happened."
"The feeling of revenge is more now than for the shrine in Samarra; that was just a building, and we can rebuild it," says Mr. Abdullah. "But what can we say about a family that has lost six members? They can only call on God for mercy. They are poor people, so have no guns and mortars to kill the others."
But many Sunnis know that plenty of guns, mortars, and rockets are in the hands of Shiite militias and death squads – some operating in uniform, under the wing of the Ministry of Interior and police – that have been responsible for the hundreds of tortured bodies, many of them Sunni, that turn up on Baghdad streets each week.
The first mortar rounds began landing in the Sunni stronghold of Adhamiyah near the revered Abu Hanifa mosque at dusk on Thursday. They fell during the night and the next day after Friday prayers, says one resident. Saturday, rumors swept the neighborhood that Mahdi Army militiamen wearing police and commando uniforms would attack; US units based in the area surrounded it with checkpoints.
"The [US] checkpoints were very good, but the people of Adhamiyah are ready – they didn't sleep that night," says one resident taxi driver, who goes by the name Abu Abdullah and lives near the mosque. One of his friends was killed in the strikes, and four were wounded.
"All the time, the people of Adhamiyah are carrying their weapons; when American patrols pass, they hide them," says Abu Abdullah. "The death squads and militias are doing the same routine since Samarra. I expect more attacks against Sunnis."
He also expects Sunni revenge for hitting the mosque. "When the rounds fell on Abu Hanifa, people were angry, and looking for mortars to shoot back ... in revenge," says Abu Abdullah. "There are no more normal people in Adhamiyah; all of them are angry."
Shiites bristle at the term "death squads," and say that Sunni militants, often linked to Al Qaeda, set the benchmark by beheading kidnap victims and targeting civilians with suicide bombs. "The crimes of the Takfiris [Sunni extremists] and Saddamists led some people to not follow the religious leaders, and get their revenge," says Abu Khadhim. "It's just reacting to crimes against Sadr City and the Shiites. The reaction that happened after Thursday was uncontrollable; people were so angry, and what can they do?"
Four Sunni mosques were burned in the Hurriyah district, and there were reports – denied by some authorities, but sworn as true by some who knew witnesses – of some Sunnis being burned alive in their homes or near mosques.
"The religious leaders made it quiet, but without the curfew there would be a disaster," says Abu Khadhim. "The people of Sadr City now are like a volcano. There were a lot of dead people."
Many in Sadr City blame US forces for this attack and others, and point to the US helicopter strike that engaged a Sadr City mortar position. The search for a US military linguist of Iraqi descent, kidnapped more than a month ago and thought to be in Sadr City, has deepened anti-US feeling.
"I think the Americans cooperate with the Sunnis for these attacks. When we try to counter-attack, the Americans stop us," says Abu Khadhim. "The Americans want Sadr City attacked, and our sons dead, and everyone to stay silent."
Prime Minister Nouri al-Maliki has also come in for sharp criticism. When he visited Sadr City on Sunday in the wake of the attacks, his motorcade was hit with stones.
"[Maliki] should protect Sadr City, and provide services, but it is winter again, with no heat or electricity," says Abu Khadhim, who says he voted for the premier. "You expect me to receive him with flowers? I don't think so."
The incident has boosted the political fortunes of Mr. Sadr, the anti-American cleric whose Mahdi Army militia has helped with everything from collecting bodies and paying for funerals to digging graves in the southern holy city of Najaf.
Some US officials have called for Sadr to be removed from the political scene and the Mahdi Army to be disbanded by force with American troops if necessary. But the Mahdi Army, like Hizbullah in Lebanon, and Hamas in the Palestinian territories, has long developed a local humanitarian effort.
Sadr loyalists hold 30 seats in the 275-seat parliament as well as four cabinet posts. The militia last Thursday arrested one bomber before his car bomb went off, and captured other gunmen.
"The Mahdi Army is doing more than the government, which has no presence in Sadr City," says Abu Abdullah, who sells perfume and shampoo in his shop. "Their popularity has increased because they prevent terrorists from bringing down Sadr City. People now think they are heroes; they are champions."