Sunni insurgents have cut the roads linking the city to the rest of Iraq. The country is being partitioned as militiamen fight bloody battles for control of towns and villages north and south of the capital.
As American and British political leaders argue over responsibility for the crisis in Iraq, the country has taken another lurch towards disintegration.
Well-armed Sunni tribes now largely surround Baghdad and are fighting Shia militias to complete the encirclement.
The Sunni insurgents seem to be following a plan to control all the approaches to Baghdad. They have long held the highway leading west to the Jordanian border and east into Diyala province. Now they seem to be systematically taking over routes leading north and south.
Dusty truck-stop and market towns such as Mahmoudiyah, Balad and Baquba all lie on important roads out of Baghdad. In each case Sunni fighters are driving out the Shia and tightening their grip on the capital. Shias may be in a strong position within Baghdad but they risk their lives when they take to the roads. Some 30 Shias were dragged off a bus yesterday after being stopped at a fake checkpoint south of Balad.
In some isolated neighbourhoods in Baghdad, food shortages are becoming severe. Shops are open for only a few hours a day. "People have been living off water melon and bread for the past few weeks," said one Iraqi from the capital. The city itself has broken up into a dozen or more hostile districts, the majority of which are controlled by the main Shia militia, the Mehdi Army.
The scale of killing is already as bad as Bosnia at the height of the Balkans conflict. An apocalyptic scenario could well emerge - with slaughter on a massive scale. As America prepares its exit strategy, the fear in Iraq is of a genocidal conflict between the Sunni minority and the Shias in which an entire society implodes. Individual atrocities often obscure the bigger picture where:
* upwards of 1,000 Iraqis are dying violently every week;
* Shia fighters have taken over much of Baghdad; the Sunni encircle the capital;
* the Iraqi Red Crescent says 1.5 million people have fled their homes within the country;
* the Shia and Sunni militias control Iraq, not the enfeebled army or police.
No target is too innocent. Yesterday a bomb tore through a party of wedding guests in Ur, on the outskirts of Sadr City, killing 15 people, including four children. Iraqi wedding parties are very identifiable, with coloured streamers attached to the cars and cheering relatives hanging out the windows.
Amid all this, Dick Cheney, the US Vice-President, has sought to turn the fiasco of Iraq into a vote-winner with his claim that the Iraqi insurgents have upped their attacks on US forces in a bid to influence the mid-term elections. There is little evidence to support this. In fact, the number of American dead has risen steadily this year from 353 in January to 847 in September and will be close to one thousand in October.
And there is growing confusion over the role of the US military. In Sadr City, the sprawling slum in the east of the capital that is home to 2.5 million people, American soldiers have been setting up barriers of cement blocks and sandbags after a US soldier was abducted, supposedly by the Mehdi Army. The US also closed several of the bridges across the Tigris river making it almost impossible to move between east and west Baghdad. Nouri al-Maliki, the Iraqi Prime Minister, added to the sense of chaos yesterday when he ordered the US army to end its Sadr City siege.
Mr Maliki has recently criticised the US for the failure of its security policy in Iraq and resisted American pressure to eliminate the militias. Although President Bush and Tony Blair publicly handed back sovereignty to Iraq in June 2004, Mr Maliki said: "I am now Prime Minister and overall commander of the armed forces yet I cannot move a single company without Coalition [US and British] approval."
In reality the militias are growing stronger by the day because the Shia and Sunni communities feel threatened and do not trust the army and police to defend them. US forces have been moving against the Mehdi Army, which follows the nationalist cleric Muqtada al-Sadr, but he is an essential prop to Mr Maliki's government. Almost all the main players in Iraqi politics maintain their own militias. The impotence of US forces to prevent civil war is underlined by the fact that the intense fighting between Sunni and Shia around Balad, north of Baghdad, has raged for a month, although the town is beside one of Iraq's largest American bases. The US forces have done little and when they do act they are seen by the Shia as pursuing a feud against the Mehdi Army.
One eyewitness in Balad said two US gunships had attacked Shia positions on Sunday killing 11 people and seriously wounding six more, several of whom lost legs and arms. He added that later two Iraqi regular army platoons turned up in Balad with little military equipment. When they were asked by locals why their arms were so poor "the reply was that they were under strict orders by the US commander from the [nearby] Taji camp not to intervene and they were stripped of their rocket-propelled grenade launchers".
Another ominous development is that Iraqi tribes that often used to have both Sunni and Shia members are now splitting along sectarian lines.
In Baghdad it has become lethally dangerous for a Sunni to wander into a Shia neighbourhood and vice versa. In one middle-class district called al-Khudat, in west Baghdad, once favoured by lawyers and judges, the remaining Shia families recently found a cross in red paint on their doors. Sometimes there is also a note saying "leave without furniture and without renting your house". Few disobey.
The Occupation: War and Resistance in Iraq by Patrick Cockburn is published this month by VersoReuse content