Leading article: Not even Saddam's death will unite Iraq now

The whole truth behind the British Army's Christmas Day assault on the so-called Serious Crime Unit in Basra may never be known. What can surely be stated with some confidence, however, is that the first, black-and-white version was incomplete; that there was more to this raid than met the eye, and that the episode as a whole has implications that do not augur well for an early withdrawal of British troops.

There can be little doubt that Basra's Serious Crime Unit presented enormous problems. This was, after all, the same building the Army had stormed to rescue two kidnapped SAS men 15 months before. If the British believed that the assault had purged the bad elements operating there, this was clearly wishful thinking. If not - and the unit's notoriety had made it, according to the Ministry of Defence, "a powerful symbol of oppression and corruption" - then the British military authorities seem to have turned a blind eye for far too long.

The building was stormed, we were told, when intelligence suggested that a large number of the prisoners known to be held there were about to be executed. We admit to a certain wariness about intelligence-led operations, given that flawed intelligence provided the Prime Minister with the official pretext for invading Iraq in the first place. Let us grant, though, that in this case the Army's prompt intervention saved more than 100 prisoners from death.

But how prompt is prompt? According to the Army, a significant number of prisoners bore signs of torture, "such as crushed hands, crushed feet, gunshot wounds to the legs and knees, electrical burns and cigarette burns". These injuries had been inflicted in premises run by British-trained Iraqi police on territory patrolled by British troops. Yet it was only when execution threatened that the British decided to take drastic action.

Disagreement has now broken out about who, if anyone, gave authorisation. The British insisted that Iraq's central government had approved it. The Iraqi army and Basra's local authorities said they could have handled the problem themselves. If even half of what is now said about the Serious Crime Unit is true, however, it was operating outside local control, as a headquarters for death squads and organised crime. Its very existence was a travesty of everything the British presence was supposed to mean in southern Iraq, and no one had been prepared to tackle it.

That it took a force comprising one in seven of the British Army in southern Iraq to destroy the unit, and that the operation as a whole is now a matter of bitter contention between the British Army, the Baghdad government and the Basra local authorities, shows that the next few months will be very far from plain sailing, even in the predominantly Shia south. A great many pitfalls lie between British ministers' hopes of an early withdrawal and their undertaking that British forces will leave only when the Iraqis are capable of ensuring security for themselves.

Recent events in and around Basra illustrate how hard this will be. The conflict is no longer between foreign troops and insurgents, nor yet between Sunni and Shia. Factionalism, warlordism, religious, ethnic and criminal rivalries are all rife. Elections have provided no shield against the mounting anarchy.

Time was when the death of the deposed leader, Saddam Hussein, might have been calculated to bring Iraqis together, but even this is no longer so. His execution - which seems inevitable after the failure of his appeal - risks exacerbating the divisions, where it is noticed at all. It is a sorry commentary on an intervention that was supposed to bring democracy to Iraq and security to the region as a whole.