By Sebastian Usher
Sunnis have been co-operating with US forces against al-Qaeda
The de-Baathification process instituted in Iraq after the Americans toppled Saddam Hussein in 2003 is now widely seen as having made bitter, new divisions in the country, fuelling the violence that has torn Iraq apart.
It also in one go stripped the country of the institutions that had governed it for decades.
Originally an American decision, the United States has increasingly tried to reverse it.
But the Shias who now dominate Iraq's government have resisted this, as they see it as just punishment for the mostly Sunni Baathists who ran the country for so long as a police state.
The Baath party was in power in Iraq from 1968 until 2003.
It is estimated that in the 1980s, 1.5m Iraqis were members.
The rise of Sunni groups opposed to al-Qaeda has spurred new optimism in Washington that Iraq may yet be salvaged from its spiral of violence
Many joined because it was the only way to get ahead in their careers.
The party's influence was felt in every pore of Iraqi society.
Only at the very top was its power weaker - there, the elite around Saddam Hussein were bound together by family and tribal loyalties rather than political ideology.
When the Americans ousted Saddam Hussein, it was the Baathists who were running the civil service, schools and hospitals.
They also constituted the army and the police.
Despite this, Paul Bremer - the man President George W Bush appointed to run Iraq - issued a ban on Baathists in public life just a month after the fall of Saddam Hussein.
It was seen as a way of breaking with Iraq's totalitarian past.
The problem for the Americans is that the most powerful political group in Iraq is now the Shia - and they have been fiercely opposed to rehabilitation of those they regard as having been their torturers and oppressors
But in the power vacuum that followed, anarchy and violence flourished.
As the security situation worsened, American policy began to change.
Disagreement over de-Baathification gradually turned into an understanding that it had failed.
Reports from Iraq made clear that it had motivated a number of Baathists to reject the new order in Iraq, with some actively fighting it with suicide attacks and bombs.
Increasingly, the US has been calling for all but the highest-level of Baathists to be given back their jobs.
Tens of thousands have been through a re-education process to achieve this.
There are no precise figures, but more than 100,000 low-level Baathists are believed to be back in their old jobs.
The problem for the Americans is that the most powerful political group in Iraq is now the Shia - and they have been fiercely opposed to rehabilitation of those they regard as having been their torturers and oppressors.
WHO ARE THE BAATHISTS?
The party was the political instrument of Saddam Hussein's rule
An estimated 2.5 million Iraqis were party members
Banned and broken up by US administrator in May 2003
Baathism was a pan-Arab secular nationalist movement
This has complicated America's efforts to win back the lost hearts and minds of former Baathists - most of them Sunni - which is seen as essential if the improvements in security in the past year are to be built upon.
The US needs them as allies in what it sees as the crucial struggle against al-Qaeda and affiliated groups in Iraq.
The rise of Sunni groups opposed to al-Qaeda has spurred new optimism in Washington that Iraq may yet be salvaged from its spiral of violence.
But if efforts are being intensified to persuade ex-Baathists that they, once again, have a stake in the new Iraq, warnings abound about the rebirth of the active political Baath party.
It appears to have rebuilt itself underground, returning to its roots as a militant group tightly organised in secretive cells.
It is unlikely any time soon to be allowed back into Iraqi political life - but there is increasing concern about the damage it can still do from the outside.