The simple question on everyone's lips is "why?" - why do Fallujah and its environs remain the most dangerous place for US forces in Iraq?
As with everything in Iraq these days, the answer depends on whom you ask. US Brig. Gen. Mark Kimmitt said the bloodshed in Fallujah was a symptom of a town "that just doesn't get it," and of a people determined to turn back the clock.
"This was a city that profited immeasurably ... under the former regime. They have a view that somehow the harder they fight, the better chance they have of achieving some sort of restorationist movement," General Kimmitt said Wednesday. Thursday, US administrator Paul Bremer promised Wednesday's killings in Fallujah "will not go unpunished."
But to Iraqi experts on the deeply clannish tribal networks of much of the Sunni Triangle, the horrifying killings and mutilation of four US security contractors Wednesday were more about a people obsessed with personal honor and revenge than evidence of nostalgia for Saddam Hussein's Iraq.
To them, the scenes were simply the extensionof a cultural clash that began soon after the US Army's 82nd Airborne Division took control of the area last spring.
"You can never forget that in this area retaliation is almost the fundamental element of the tribal system, its focal point,'' says Sadoun al-Dulame, a Baghdad-based political scientist who grew up in the area as a member of the Dulame tribe, one of its largest. "This is a revenge culture where insults to people's honor will always be repaid with violence."
The 82nd Airborne is handing control of the area to the Marines, and coalition officials say the transitional period may have led to the fillip in violence, with insurgents testing new troops' resolve. In addition to the four contractors, five US troops were killed by a bomb on the same day. March has been the second-deadliest month for US troops in postwar Iraq, and officials are bracing for more, ahead of the anticipated June 30 handover of Iraqi sovereignty.
Mr. Bremer vowed Thursday that the Fallujah attacks will not "derail the march towards stability and democracy."
A solution to the trouble in Fallujah lies in what form that democracy will take. If the transition plan for Iraq being crafted by the US, the UN, and Iraqi partners convinces Sunni towns like Fallujah that their interests will be protected in a new Iraq, likely to be dominated by the Shiite majority, they will eventually lay down their weapons, even if it means giving up age-old Sunni control of Iraq.
But crafting the plan and getting buy-in from deeply suspicious citizens in towns like Fallujah will take time, with most analysts saying the most optimistic timeframe is about a year.
Fallujah is far from the only place where tribal traditions are strong, or where support for Mr. Hussein's regime ran deep. In Sunni Triangle towns like Ramadi, Bayji, and Tikrit, Hussein's hometown, many of the same variables are at play. But none of these towns have the local support or savagery of attacks seen in Fallujah.
Amatzia Baram, an Iraq expert at the US Institute for Peace in Washington, points to a challenging confluence of factors in Fallujah. Like a number of towns in the Sunni Triangle, Fallujah has a large number of residents from Saddam Hussein's Albu Nasser tribe, and a high percentage of people who served in his armed forces and intelligence forces. But what makes Fallujah different, Dr. Baram says, may be Sunni Islam.
The town is deeply Islamic, and strongly influenced by the Salafy traditions of neighboring Jordan, Syria, and Saudi Arabia, a factor he attributes to its position on the Euphrates, which flows from Syria and has provided an umbilical cord to the Moslem world since the Islamic conquest.
Tigris River towns like Tikrit, more influenced by Turkey, are less religious in outlook and don't share the motivation taken up by Fallujah since the invasion. So while Tikritis have not replaced the old rallying cry of "Our blood and souls to redeem you, O Saddam,'' crowds in Fallujah today regularly chant an adapted version: "Our blood and souls to redeem you, O Islam."
"It's gone beyond 'you killed my cousin so I have to kill you.' '' says Baram. "It's about religion."
That means the trouble in Fallujah could outlast the US presence. "Their motivations and political ideas are going to extend far beyond this period,'' says Nadhim Jissoor, a political scientist at Baghdad University. "If the right balance isn't struck, the people of Fallujah might very well resist a central Iraqi government."
For now, the US military is in a bind. Baram says one of the biggest problems in Fallujah is a fundamental cultural difference in how to wage war.
"If I kill someone from your tribe, I know another member of my tribe will definitely be killed,'' he says. "But people in Fallujah have learned that when they kill Americans nothing much happens. They learned that the Americans have different values, and this makes killing an American less dangerous than killing someone from another tribe."
Retaliation also has a price. US military commanders mulled options Thursday with few signs of US activity in the city. "If you hit the whole city, you will simply be expanding the circle of your opponents,'' says Dr. Dulame. "There's not much the Americans should do now but withdraw."
Since May 2003, Fallujah has been a staging area for attacks that have killed US troops and foreign contractors. About 100 Iraqi civilians have also died in area conflict since that time.
March 31, 2004: Four US security contractors killed, their bodies mutilated. Five US soldiers killed.
March 26: US firefight kills four militants.
March 25: 1 marine killed in ambush.
March 24: Ambush injures two US soldiers and three civilians, three others killed.
Feb 14: Insurgents attack Iraqi police station, killing 23 Iraqis.
Feb 12 : Attack on convoy carrying US Gen. John Abizaid.
Jan. 24 : Two soldiers killed by explosive device.
Jan. 6 : Two French nationals killed after car breaks down in city.
Jan. 8 : Nine soldiers killed when helicopter crashes south of Fallujah.
Jan. 2 : Soldier dies in helicopter shootdown.
Dec. 28 : Soldier killed by explosive device.
Nov. 8 : Soldier killed by explosive device.
Nov, 2 : 16 soldiers die when Chinook helicopter is shot down.
Oct. 28 : Soldier killed in "nonhostile" gunshot incident.
Oct. 20 : Soldier killed by explosive device.
Sept. 14 : Soldier killed by explosive device.
August 27 : Soldier killed by explosive device.
July 18 : One soldier dies, three injured by explosive device.
June 5 : One soldier killed, five wounded in grenade attack.
May 27 : Two soldiers killed, nine wounded in grenade and gun attack.
May 1 : Seven US soldiers wounded.
April 30 : US troops fire on Iraqi civilians for second time as crowd protests a shooting.
April 28 : 13 demonstrators shot dead.
Sources: BBC, Stratfor, The Guardian, Iraqbodycount.net. Civilian counts are based on at least two media reports.