The violence south of Baghdad isn't just an uprising against the American occupation. It is a struggle for the leadership of Iraq's Shia Muslims. If they get this wrong - and all the signs are that they will - the Americans
risk driving the Shias into the arms of a radical who until now had little support.
When the fighting in southern Iraq started, I called a friend who lives in the holy Shia city of Karbala. As a follower of the much-revered Ayatollah Ali al-Sistani - the most senior cleric in Iraq, who advocates separation of the spiritual from the political - he dislikes Moqtada al-Sadr's call for violent Islamic revolution. But since the Americans closed down al-Sadr's newspaper and arrested one of his aides, my friend has been finding it difficult to hold his line. "You have to understand our tribal system," he explained. "If someone in a family is killed, others will start to use their weapons. So it's not just al-Sadr's people now, it's everyone. We see this operation as against all Iraqis."
Several Iraqi tribes incorporate both Shias and Sunnis, so the current unity (however temporary) between the two sects is not surprising. Moreover, most Iraqis are united by their nationalism.
According to a Shia academic who has met him, al-Sadr is wild-eyed, unstable, and probably only in his mid-twenties. His standing derives entirely from his family, and especially from his father, a grand ayatollah murdered by Saddam Hussein's regime in 1999. In Iraq, who your father was matters a lot - but so does your age if you are a religious scholar, and al-Sadr has no status as a cleric. He trades on support from angry, unemployed young men, and a hardline faction in Iran. His mentor, Ayatollah Kazem al-Haeri, is an Iranian close to that country's supreme leader, Ayatollah Ali Khamenei. They have dubbed al-Sadr "the new Nasrallah" - a reference to the leader of Hezbollah, another Iranian-backed group, which achieved notoriety in the 1980s for hostage-taking in Beirut.
Bob Baer, a former CIA agent who operated in Iraq and Lebanon, told me that Hezbollah cadres have been training al-Sadr's Mahdi army inside Iraq for nearly a year, and have resolved to drive the Americans out of Iraq as they drove the Israeli army out of southern Lebanon. All of which would be bad for the US, except that most Iraqis do not want an Islamic state under the leadership of a volatile young man.
Foolishly, senior American officials - including the defence secretary, Donald Rumsfeld, and Vice-President Dick Cheney - have described the fighting as a "test of wills": al-Sadr knows that all he has to do to win is be more obdurate. In fact, it's a test of diplomatic and political skills. The British - canny old colonialists that they are - managed to negotiate a peaceful end to the siege of the governor's office in Basra at the beginning of al-Sadr's uprising. If the Americans can step back and give senior Shia members of the Iraqi Governing Council enough time to work with Ayatollah al-Sistani, al-Sadr could probably be contained and neutralised. But by repeating the mantra that they will not negotiate with "terrorists and thugs", the Americans are backing themselves into a corner. Getting al-Sadr to relinquish his revolution will involve doing a deal, possibly allowing his newspaper to reopen, or even rescinding the warrant for his arrest, but the Americans do not seem to understand that doing deals is what works in Iraq.
Even if this crisis passes, Americans can do little to change the contradictions at the heart of Iraqi attitudes. A year ago, a political scientist described to me how he had stood in his basement, raging as the US tanks rumbled overhead. "Why could the Iraqi army not have done this?" he lamented. Most Iraqis I know feel simultaneously relieved that the Americans overthrew Saddam Hussein and humiliated that their nation has been occupied. The pro- and anti-war camps - polarised and strident in the US and Britain - are contained inside the head of nearly every individual Iraqi. People are desperately trying to make sense of the uncontrollable forces that dictate their lives - 30 years of dictatorship, three wars and now occupation. Some Americans working outside the confines of their concrete and razor-wired headquarters in Baghdad understand this.
But such complexity does not seem to filter up to the decision-makers.
In the film Fog of War, the former US defence secretary Robert McNamara, who served under Kennedy and Johnson during Vietnam, cites "understand your enemy" as the first lesson of war. The current administration has not only failed to learn that lesson, but seems to work actively against it. Yet without understanding it, the US has no chance of predicting the actions of either its enemies or those who are still - against all odds - trying to be its friends in Iraq.
Lindsey Hilsum, international editor of Channel 4 News, will be writing a fortnightly column for the NS