A machine-gun chattered just outside the gate of the biggest hospital in Mosul just as Dr Ayad Ramadani, the hospital director, was saying he blamed the Kurds for the orgy of looting and violence which had engulfed Iraq's northern capital. "The Kurdish militias were looting the city," he explained. "Today the main protection is from civilians organised by the mosques."
This is not quite fair on the Kurds, since Arabs were also doing their fair share of looting in Mosul over the past few days, ransacking everything from the Central Bank to the university. But there is no doubt that the Arabs, who make up three-quarters of Mosul's population, are blaming the Kurds for devastating their city.
The downfall of Saddam Hussein has exacerbated, to a degree never seen before, the ethnic and religious tensions between Kurds, Sunni Arabs and Shia Arabs, the three great communities to which almost all Iraqis belong. But, deep though differences were between them in the past, there is little history of communal violence in the country on the scale of Protestants and Roman Catholics in Belfast or Muslims and Christians in Beirut.
This may now be changing. Much of the looting in Baghdad has been by impoverished Shias from great slums like Saddam City attacking the homes of wealthier Sunnis, who have traditionally made up the establishment.
The United States has a lot to answer for in allowing the violence to continue for so long. In Baghdad, American troops were notoriously inactive while shops and homes were being looted. In northern Iraq, mobs of looters were able to take over Mosul because almost no American soldiers were present. The reason for their absence was that the US had rushed 2,000 men, most of its slender forces in the north, to take over the Kirkuk oilfields. Only a few hundred soldiers were available for Mosul. The chants of anti-war protesters about how the conflict is all about control of Iraqi oil do not seem as over-stated today as they did a month ago.
The failure of the US Army to stop the looting is only the latest manifestation of a theme evident in American policy before and during the war. Although the conflict was being justified as a fight to liberate the Iraqi people, their involvement was discouraged and their existence ignored. According to one Iraqi who met George Bush just before the war, the President was intrigued to learn, apparently for the first time, that Iraq was inhabited by two sorts Muslims, Sunnis and Shias, with deep differences between them.
Some of the ethnic and religious conflicts emerging should not come as a surprise. Soon after the British captured Baghdad in 1917, the civil commissioner, Captain Arnold Wilson, wrote a plaintive note to London, arguing that the new state being created out of three former Turkish provinces could only be "the antithesis of democratic government". This was because the Shia majority rejected domination by the Sunni minority, but "no form of government has been envisaged which does not involve Sunni domination". The Kurds in the north, Wilson prophetically pointed out, "will never accept Arab rule".
It is important not to project these arguments too far into the future. Iraqi nationalism did develop after British occupation. Iraqi Shias, the majority in the Iraqi army, did fight against Shia Iran during the Iran-Iraq war. Kurdish leaders today do recognise that, surrounded by hostile powers, full independence for Kurdistan is not feasible. Real autonomy within Iraq, and a share of power in Baghdad, is the better option.
Iraqi liberals often argue that the extent of communal differences in Iraq has been exaggerated and violence experienced by Shia, Sunni and Kurd has come from the government in Baghdad. They point out that neither the Sunni nor the Shia communities are monolithic and, in any case, Saddam Hussein stoked communal differences to his advantage.
Some truth is evident in this, but even Iraqi opposition politicians who have argued this optimistic view to me soon start talking about Shia, Sunni and Kurd as if they were immutable categories. Saddam Hussein's state was always deeply sectarian. On the day Kirkuk fell I talked to 10 Iraqi army deserters, all private soldiers, who had been defending a large village. Nine of them were Shias from the south of Iraq and one was a Turkoman. Although they came from different units, not one of the soldiers had met a Sunni Muslim who was a private soldier or a Shia who was an officer.
The history of the past 30 years has exacerbated ethnic differences. For instance, Kurds in the northern three provinces, which have had de facto independence for 12 years, seldom now speak Arabic. Six weeks ago I was speaking to about 100 peshmerga, as Kurdish soldiers are known. (This started off as a private interview with their commanders, but in true democratic spirit their men gathered round to shout agreement or disagreement). When I asked how many spoke Arabic as well as Kurdish only three put up their hands.
In 1991 the Shias and Kurds rose against President Saddam but the Sunni heartland did not. In the following years, Shia religious leaders within Iraq were systematically assassinated and their followers persecuted. I used to think that Sunni or Christian friends in Baghdad were exaggerating when they expressed terror at what would happen if the Shias of Saddam City in east Baghdad or in the south ever revolted, but it turns out that they were right.
What has given such a terrible edge to these differences is the economic misery of most of the Iraqi population. Many of the looters in Kirkuk and Mosul were triumphantly bearing home almost valueless stolen goods like broken pieces of corrugated iron or shabby old chairs. In Kurdistan, often presented as doing better than the rest of Iraq, 60 per cent of the population would be destitute without the food rations provided by the United Nations' Food-for-Oil Programme.
With so many Iraqis living on the edge of starvation, it is hardly surprising that they took the one chance they had over the past week to loot anything they could get their hands on. Over the past 12 years in Baghdad you would see men standing all day in open-air markets trying to sell a few cracked earthenware plates or some old clothes. They were the true victims of UN sanctions while Saddam Hussein could pay for gold fittings to the bathroom in his presidential palace.
Economic sanctions really did devastate Iraqi society. In one village, called Penjwin, in 1996 I found that villagers were surviving by defusing a particularly lethal Italian landmine, called the Valmara, in order to sell the scrap of aluminium in which the explosives were wrapped. The number of unemployed and semi-employed people and criminals in Iraq soared during the 1990s. Looking forward to the transition period after Saddam Hussein, the Brussels-based International Crisis Group noted three weeks ago that "this amorphous social group could become an important source of violence and disorder during the transition, expanding the ranks of any destructive mobs."
For all the crimes of Saddam Hussein, the greatest reality in the lives of most Iraqis for over a decade has been this economic devastation. It is their terrible poverty which has given such an edge to the fury of the mobs of looters which have raged through Iraqi cities in recent weeks. It is exacerbating religious and ethnic tensions which otherwise might lie dormant. Unless the Iraqi poor feel their lives are improving, the US and Britain - now responsible for Iraq - may soon find that they too have become a target for their rage.
The writer is the co-author, with Andrew Cockburn, of 'Saddam Hussein: an American Obsession'