Every time I return to Baghdad the ugliness hits me – the tattered plastic bags trapped in endless coils of razor wire, the miles of ugly concrete blast barriers, the sandbags, checkpoints, ubiquitous guns. The roads are pitted, the pavements crumbling, the cars ancient. Saddam-era ministries and palaces bombed in 2003 still stand abandoned, gaping holes in their flanks. The showpiece hotels are empty. The fancy shops are shut. Rubbish piles up. Water and electricity grow increasingly scarce. Statues are broken. The traffic lights have not worked in years. Billboards have collapsed.

There is nothing new or colourful in the city, nothing of beauty. There are no cinemas or theatres still open, no fountains, no zoo, no car dealerships, shopping malls or well-kept parks. The background noise is not of music, birdsong or children’s laughter, but of generators, helicopters and bursts of gunfire. Its inhabitants hurry home before dusk. It is a baked, dusty, joyless city from which those who can have fled, a city where the preoccupation of those that remain is survival, a city in a seemingly terminal state of neglect and decay. On the flight from Jordan I sat next to a young Iraqi Ministry of Agriculture employee who was returning from five months training in Australia. He had been tempted to stay, but could not abandon his family. “I come back here to die,” he said.

It is small wonder that in such an arid, bleak environment any green shoot causes excitement, and in the past few months there has been rare cause for hope. General David Petraeus, the top US commander in Iraq, will doubtless highlight it today when he gives Congress his verdict on George Bush’s troop surge strategy. Sunnis in much of western and central Iraq, including Baghdad, have turned on the foreign-led al-Qaeda jihadists who arrived in their communities promising to eject the infidel Americans. What they actually did was impose a rule of terror, whipping or executing any who opposed their extremism.

The tribal leaders of Anbar province led the way, encouraging thousands of their followers to join the hated Iraqi police and make common cause with the equally reviled US military. Anbar, once the heart of the infamous Sunni Triangle, is now one of the safer provinces in Iraq – so safe that Mr Bush visited it last week. The US military is now trying to replicate the success of Anbar in other Sunni areas by recruiting thousands of Sunni males into groups of “concerned citizens” determined to take back their neighbourhoods.

Iraq timeline: five years of conflict

From accusations that the weapons of mass destruction dossier had been sexed-up to withdrawal of British troops from Basra

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US generals claim to have al-Qaeda on the run, to have deprived it of the strongholds where it planned its car bomb spectaculars, to have achieved “tactical momentum”. Al-Qaeda attacks have certainly fallen off in recent months, and appear increasingly to be aimed at soft and remote targets such as the unfortunate Yazidi sect who live near the Syrian border: truck bombs killed 500 on August 14.

This “Sunni awakening” is an astonishing development, but as far as bragging rights go it has its limits. For a start, it began months before the “surge”, though the deployment of an additional 30,000 US troops probably emboldened more ordinary Sunnis to tackle the extremists in their midst.

More importantly, it has done little to remedy Iraq’s most pressing problem – its sectarian civil war. The anti-American insurgency may be finally losing heat, and al-Qaeda may be off-balance, but those Shia-Sunni emnities that al-Qaeda ignited through deliberate slaughters of Shias show no sign of abating.

The surge has managed to contain those emnities. It has reduced the sectarian violence significantly by moving US troops out of their huge bases and into 29 combat outposts in Baghdad’s worst troublespots. But while it has largely frozen the battle lines in place, there has been little corresponding effort to reconcile Shia and Sunni and heal those festering hatreds.

The Shia-led Government was supposed to have used the breathing space provided by the surge to reach out to the Sunni minority, and to establish itself as a trusted government of national unity. Unfortunately Nouri al-Maliki, the Prime Minister, is no Nelson Mandela. Only belatedly, and under heavy US pressure, has the Government made a few conciliatory moves, relaxing restrictions on ex-Baathists taking senior government jobs and sending money to Anbar for reconstruction.

America’s new Sunni allies still regard the Government with profound suspicion, as a puppet of Iran. Most Sunnis have come to rely – irony of ironies – on US troops for protection. At the same time an increasing number of Shias, especially in Baghdad, look to the al-Mahdi Army militia, not the hapless Mr al-Maliki, to provide security and basic services. Far from establishing itself, the national Government is flirting with irrelevance. Even at the best of times most Iraqis put loyalty to tribe or sect above loyalty to the artificial construct that is their country.

Whatever Congress decides, the overstretched US military cannot sustain the surge much beyond next spring. That poses several questions in a capital and country that has increasingly become a patchwork quilt of deeply antagonistic, ethnically cleansed Sunni and Shia enclaves.

Will the violence return as US troops leave? Has their presence merely driven the fighters into other areas? To what extent has al-Qaeda disappeared, or is it merely lying low? Is the slowly improving Iraqi Army anywhere near ready to take the strain? Will the new Sunni police forces and “concerned citizen” groups simply metamorphose into well-armed, well-trained militias?

I spent two days last week in Ghazaliyah, a district of western Baghdad that was a sectarian war zone until the soldiers of the surge moved in. Outwardly, Ghazaliyah is now a success story. Decapitated or disembowelled bodies no longer turn up on the streets each morning. Exiled families have returned to homes on the sectarian fault line that divides the Shia north from Sunni south. Markets have reopened amongst the debris, pools of backed-up sewage and accumulated garbage. It is wonderful to behold, but nobody deludes themselves. There is no contact between the two communities. A Shia still risks his life by talking to a Sunni, and vice versa. Sunni and Shia families both say they will flee again the moment the US troops depart.

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