Iraqi Shia are divided in their response to the outbreak of violence between coalition forces and the supporters of cleric Moqtada Sadr.
By Roger Hardy
BBC Middle East analyst
Some are being swept along on a tide of angry anti-Americanism but others draw the lesson from events of 80 years ago when Iraqis rose up against British colonial rule.
That revolt resulted in the British simply entrusting the government of Iraq to a Sunni elite - a pattern which continued until the fall of Saddam Hussein's regime last year.
Shia militiamen in Basra occupied the governor's house in April
Comprising some 60% of all Iraqis but long ruled by Sunnis, the Shia have long felt themselves to be an underclass.
But for all their sense of communal solidarity, they are not homogeneous.
One divide is between the religious and the secular.
Another is between the political activists and those who favour keeping out of politics.
In the second category is Ayatollah Ali Sistani, the most senior religious figure in the Shia holy city of Najaf, who has so far been cautious in the public statements issued in his name.
Whatever he may be feeling privately, the ayatollah clearly has no wish to be seen taking America's side at a time when Shia blood is being spilt.
Among the activists, three main trends are apparent:
- The Sadr group
- The Daawa party
The Sadr group
This group represents a radical, home-grown trend which some see as a force to be reckoned with. It is named after a popular religious figure, Ayatollah Mohammed Sadeq Sadr, who was assassinated - apparently by agents of the Saddam regime - in 1999.
The group is now led by the ayatollah's 30-year-old son, Moqtada Sadr.
The chief US administrator in Iraq, Paul Bremer, has said he will not tolerate the activities of the radical cleric.
He was speaking after violent confrontations between the cleric's supporters and US-led forces in both Baghdad and parts of the south.
US forces are committed to capturing or killing Moqtada Sadr
Mr Bremer told journalists that the cleric was, as he put it, trying to establish his authority in place of the legitimate authority, and that this would not be tolerated.
Moqtada Sadr has been a thorn in the Americans' side ever since they overthrew the Saddam Hussein government a year ago.
He is young and his base of support is relatively small.
Yet he comes from an illustrious Shia religious family, and his fiery speeches denouncing the American occupiers of Iraq strike a chord - especially among the young.
It is also popular in Baghdad's Shia suburbs, the biggest of which, Saddam City, was swiftly renamed Sadr City after the war.
The Daawa party
Founded in the 1950s, the Daawa party is the oldest of the Shia Islamist movements.
After a series of attempts to assassinate Saddam Hussein and some of his ministers, it was harshly suppressed and eventually split into several factions.
A senior Daawa figure, Sheikh Mohammed Nasseri, returned to southern Iraq from exile in Iran as part of an attempt by the party to re-establish itself after years of clandestine existence.
The Supreme Council for the Islamic Revolution in Iraq is a Tehran-based group, founded in 1982 and headed by Ayatollah Mohammed Baqr al-Hakim.
He was killed along with about 80 people by a car bomb in the holy city of Najaf in August last year.
Sciri may be finding the Iranian connection a liability rather than an asset. Twenty years ago Iraqi Shia were more excited about the Iranian revolution than they are today, when it has lost much of its fizz.
Spectre of sectarianism
Some Iraqis from the country's Sunni and Christian minorities have been uneasy about the new mood of Shia resurgence.
They fear that, in the new climate, the Shia will demand not just an end to their oppression but a dominant role in the new order.
That would trigger Sunni alarm in Iraq - and among the predominantly Sunni ruling elites in the Arab world.
At root, the question is whether the factors that divide Iraqis will prove stronger than the factors that unite them.
Anti-American demonstrations have witnessed the slogans "No Sunni, no Shia - only Islamic unity".
Most Iraqis are indeed united by allegiance to a common faith - and by shared suffering under Saddam's rule.
Intermarriage between Sunni and Shia is commonplace. Both communities share a sense of Iraqi national pride.
A crucial issue is whether the Shia, or a significant number of them, will press for Iraq's transformation into an Islamic state.
Most Iraqis, and many Shia, seem to favour the separation of religion and state.
But if the Americans continue to antagonise the Iraqi population, the Shia could be further radicalised and foment unrest - with potentially damaging consequences for both Iraq and the region.