KEY POINTS:
For once, George W. Bush's open-faced incomprehension - at Nouri Maliki's decision to set off a civil war inside Iraq's Shiite community - seems entirely appropriate.
When the United States President admitted he did not know why the Iraqi Prime Minister had launched an offensive in Basra, saying "I'm not exactly sure what triggered the Prime Minister's response", he was not alone.
Bush sought to bolster Maliki by saying his Government faces a "defining moment in the history of a free Iraq" and that the crackdown "is a necessary part of the development of a free society".
But the consequences of Maliki's decision to send 15,000 Iraqi troops, and as many policemen, into Basra has been the destruction of a nine-month-old ceasefire from Moqtada al-Sadr's Mehdi army. In just a few days it has swept back on to the streets in Kut, Hillah, Amara, Karbala, Nasiriyah, and Diwaniya, as well as into Sadr City in Baghdad, where militiamen have been raining rockets and mortars on the Green Zone.
Iraqi officials said at least 220 people had been killed in southern Iraq and 550 injured. In Baghdad, the Health Directorate said the number raised to 90 killed and 480 injured in clashes and by US air strikes in Sadr City. The district's two hospitals, serving its 2 million people, are overflowing and understaffed.
In Basra, British troops have been supporting the Iraqi troops who have been struggling to take ground against the Iranian-backed militia.
American jets have been in action supporting the Iraqi Army and there is even talk of US troops being sent south into what has been a British-run zone.
The ceasefire with Sadr has been an essential part of the success of American General David Petraeus' "surge" - the deployment of an extra 28,000 US troops into Baghdad and nearby cities.
Assured of quiet on the Shiite front, US forces were free to concentrate on battling al Qaeda and Baathist insurgents among the Sunni community.
Petraeus is due to testify before the American Congress in two weeks' time, where he was expected to show his favourite slide - a graphic illustration of the steady decline in fighting and terror attacks since the surge. A new slide will now have to be prepared, showing an upturn in violence.
There is now a very real danger that with an explosion of violence among the Shiites, the rival Sunni, concentrated in and around Baghdad, will feel threatened by a return to sectarian bloodletting and break off deals with the Americans to purge their ranks of foreign al Qaeda fighters.
With less than a third of Basra under government control, and insurrection across much of the rest of the south, it looks like the beginning of the end of the Maliki Government.
Maliki's confident prediction that he would crush the Mehdi army is turning out to be a dangerous gamble that is fast eroding his authority. It is politically damaging to Bush, who had claimed the "surge" had effected a turning point in America's five-year-old war to pacify Iraq.
The Republican prospective-nominee, Senator John McCain, is a strong supporter of the surge whereas his opponents, Senator Barack Obama and Senator Hillary Clinton, want to bring US troops home.
Bush had praised the surge as showing that the Iraqi security forces, trained and supported by the US, could at last stand and fight on their own. So far, the gunbattles are providing evidence that exactly the opposite is true.
About 40 policemen handed over their weapons to the Mehdi army in Sadr City, said one of the policemen. "We can't fight our brothers in the Iraqi Mehdi army," he said.
Sadr's militia is believed to number 60,000. He pulled out of a ruling coalition of Shiite parties, including Maliki's Dawa Party, last year in protest at the government's refusal to set a date for American withdrawal.
The faltering Basra assault by Iraq's Army and police has been billed by the Iraqi Prime Minister as an attack on "outlaws". But the other two main Shiite militia, the Badr Brigade of the Supreme Islamic Iraqi Council, and the Fadhila party, appear to have been left untouched.
All three have been vying for control of Basra's oil riches for months, since before British troops pulled out of the city, and withdrew in an "overwatch" role to the local airport in September last year.
The Badr Brigade has a long association with neighbouring Iran, where its leadership was based during Saddam Hussein's regime. And all three militia have been accused of murder, torture, and extortion as they have fought over the region's export of 1.54 million barrels of oil a day, which provide 80 per cent of Iraq's government revenue.
Provincial elections are scheduled for October in southern Iraq and Maliki's critics have suggested that, by attacking the Mehdi army, he is trying to smash his most potent opponents within the Shiite community, which make up the majority of Iraqis.
Attempts to do so will be undermined by incidents such as an American or British air strike against a house in Basra's Hananiyah neighbourhood yesterday, in which news agencies reported eight people were killed and another seven injured. It was not clear yesterday if the dead were fighters or civilians. If they turn out to be the latter, there is a danger that other Shiite groups will join the street fighting in revenge against the Iraqi Army, which is already perceived as doing the bidding of America in its attempts to clean up Basra.
"We are aware of reports of incidents in the Basra area resulting in civilian casualties," said Major Tom Holloway, a British military spokesman. "We are investigating those reports and do not have any further details at this time."
Television footage showed smoke rising from Hananiyah. Pools of blood and a destroyed pick-up truck were seen outside the home hit by the plane.
Iraqi authorities extended a curfew in Baghdad indefinitely and in a sign of the escalating stakes, Maliki called Sadr's fighters "worse than al Qaeda".
Yesterday, Sadr appeared to be reaching out to both Sunni and Shiite Muslims with a call, during an interview with al-Jazeera television, to Arab leaders to back resistance against foreign occupation. His rally cry raises the spectre of a double front, Shiite and Sunni, against the American-led foreign armies in Iraq.
Iraq's own Government is unlikely to be able to sustain violence between the Shiite-dominated armed forces and Shiite militia.
Sadr's senior aide, Salah al-Ubaidi, said there has been contact with Grand Ayatollah Ali al-Sistani and both men have the interests of ending violence in Iraq at heart.
THREE SIDES OF THE SHIITE SPLIT
MEHDI ARMY
Founded in 2003 by the Shiite cleric Moqtada al-Sadr following the American-led invasion of Iraq, the Mehdi army and factions within it have been the most active in armed conflict against the occupation of Iraq. Sadr, son of Iraqi Shiite cleric, the late Grand Ayatollah Mohammed Sadeq al-Sadr, was implicated in the murder of a rival cleric early in the occupation. Trading on both his famous name and the security vacuum in post-invasion Iraq, the organisation quickly built up a formidable following, both politically and as a militia. A period of armed conflict with US troops in 2004 - the first major outbreak of Shiite anti-occupation violence - was negotiated into a patchy ceasefire. The organisation was heavily implicated in anti-Sunni death squads with equally intermittent periods of ceasefire. Prime Minister Nouri Maliki was blamed by the US for preventing moves against the militia earlier. The decision to attack the Mehdi army follows the further descent of Basra into anarchy since Britain handed over operational responsibility to Iraqi forces last year. In some areas the police forces have been heavily infiltrated by Sadrists.
SCIRI/SIIC
Founded in 1982 during the Iran-Iraq war, the Supreme Council for Islamic Revolution in Iraq - whose military wing was the Badr Brigades - was a powerful exile group based and trained in Tehran. After the invasion and the return of council leaders to Iraq, many believed it would become the dominant force in Iraqi Shiite politics. Many younger Shiites became disillusioned with the council believing it was "too Iranian" and was too close to the US-led occupation. The council and the Mehdi army have been involved in a long struggle for influence and power in the south where the council has dominated more formal political structures. Unlike the Mehdi, its Badr Brigades were integrated, superficially at least, into the security forces.
AL-FADHILA
The Islamic Virtue Party is the third major Shiite faction in Basra and follows Ayatollah Muhammad Yaqoubi, a student of Mohammed Sadeq al-Sadr. Although affiliated it is not a member of his Sadrist movement. Sadr's movement and al-Fadhila have been in political conflict over Iranian intervention in Iraqi affairs - like the Supreme Council the Mehdi army enjoys the tutelage of Iran - and over control of the southern cities including Basra whose Governor Mohammad al-Wai'ili was a member of al-Fadhila. With the political scene in Basra and elsewhere dominated by assassination and intimidation it is hard to tell who has been behind some of the acts of inter-Shiite political violence.
- OBSERVER, additional reporting Independent, Reuters