By Heather Sharp
BBC News Online
The US-led coalition's task of building a new political structure in Iraq has meant negotiating a complex network of power struggles and a potentially explosive mixture of religious, political and ethnic groups.
This has been further shaped by the increasing resentment of the occupation - some of the Iraqis engaging with the US-driven political process have watched their credibility drop and faced the threat of violent attacks.
Ayatollah Ali Sistani is Iraq's most senior Shia cleric
Since the fall of Saddam Hussein, the previously oppressed majority Shia Muslims have risen to gain influence that reflects their 60% share of the country's population.
Many Shias look to the most senior - and very popular - Iraqi Shia cleric Ayatollah Sistani for leadership.
There are also two main religious Shia parties, the Supreme Council for the Islamic Revolution in Iraq (Sciri) and the Daawa Party.
As Sciri and Daawa have worked with the coalition on the US-appointed Governing Council, a sizeable minority of Shias, particularly the poor and disenfranchised, have united behind the radical young cleric, Moqtada Sadr.
The radical cleric has led uprisings against US forces centred on Najaf.
Weeks of fighting began in April 2004, to abate only when a fragile truce was agreed after the mediation of Iraq's senior Shia cleric, Grand Ayatollah Ali Sistani.
Fresh clashes erupted in the holy city in early August, which again required the ayatollah's intervention.
Most analysts agree that the ceasefire, established at the end of August, leaves Mr Sadr strengthened politically and barely dented militarily.
Moqtada Sadr is popular among poor and disenfranchised Shias
Meanwhile, the minority Sunni population, from whom the Iraqi political elite has historically been drawn, have seen their influence eroded.
Swathes of former members of Saddam Hussein's Baath Party - many Sunnis - have been sacked from jobs as teachers, soldiers and civil servants.
Sunni militants are thought to be behind some of the worst insurgent violence, much of which has taken place in mainly Sunni areas.
The resulting heavy coalition crackdowns and slowed reconstruction have, in turn, further angered and disenfranchised the Sunni population.
Moves to re-instate former Baath party figures to handle security in restive Sunni areas such as Falluja appear to have helped, but have been anathema to others who have struggled for years to see Saddam Hussein's regime removed.
Some influential members of the Governing Council were moderate Sunnis, including Ghazi Yawer who has become president in the interim government, and the secular democrat Adnan Pachachi who was considered a likely contender for the same position.
But credible religious voices representing the Sunnis in politics have been slow to emerge, although Sunni clerics in the Muslim Ulema Council are becoming increasingly vocal and have teamed up with some influential Shias to oppose the occupation.
The emerging Iraq-based leaders have faced competition from returning exiles who opposed Saddam Hussein's regime from the safety of London and Washington.
Ahmed Chalabi of the Iraqi National Congress and Iyad Allawi of the Iraqi National Accord were barely known in Iraq and have struggled to establish credibility in the face of deep suspicion because of the strong US backing both have enjoyed.
Chalabi was said to be the Pentagon's favourite to lead Iraq
Mr Chalabi, once the Pentagon's favoured candidate to lead Iraq, has fallen from favour dramatically amid allegations of links to Iranian hardliners and concerns that he provided faulty intelligence in the run-up to the war.
In March, Washington stopped payments to the INC and raided Mr Chalabi's house, and in August, an Iraqi judge issued an arrest warrant for him over an alleged counterfeiting operation.
Mr Chalabi denies the accusations and has since claimed that the charges have been dropped.
In contrast, Mr Allawi, who has been critical of the coalition but is said to be close to the CIA, has been appointed prime minister in the interim government.
Iraq's Kurds - 15-20% of the population - have been battling to defend the autonomy they enjoyed under US and UK protection during the 1990s.
Although many Kurds' ultimate desire is for full independence, their leaders have committed to campaigning for the protection of their rights within a united and federal Iraq.
The Kurds gained ground when Shia leaders eventually backed down in a conflict over a clause in the Iraqi interim constitution which effectively gave them a veto over a permanent constitution.
But they have been angered by the fact that the UN resolution which outlines the terms of the handover of power from coalition to Iraqi leaders does not mention the constitution.
Kurds were well represented on Iraqi Governing Council and hold several seats in the new interim government, including vice president and foreign minister.
But, with a long history of persecution by Iraqi governments, they are still calling for stronger guarantees of their autonomy and are unlikely to fully disband their peshmerga militia for some time.
Iraq's Turkmen and Assyrian minorities have also been organising themselves politically, were represented on the Governing Council and hold seats in the interim government.