The Iraq Inquiry is resuming public hearings following the Christmas break, with further evidence about the efforts to stabilise the country in the wake of the 2003 invasion.
Throughout the week, the inquiry will take evidence from senior officials and military officers before moving on to the politicians - including former Prime Minister Tony Blair - later in the month.
The first witnesses include Gordon Brown's foreign policy adviser Simon McDonald and the former ambassador to Baghdad, Sir William Patey.
Although much of the public interest has centred on Mr Blair's original decision to go to war, the inquiry has taken extensive evidence on the lack of planning for the aftermath of the invasion which saw Iraq descend into chaos.
In the final session before Christmas, inquiry chairman Sir John Chilcot strongly defended the way it was operating in the face of criticisms that the questioning of witnesses was too gentle and not sufficiently probing.
He said that they were not there to provide "public sport or entertainment" and that they had already uncovered a huge amount of "valuable and illuminating evidence".
Sir John also insisted that there had been "an exceptional level of openness" and that he remained committed to taking as much of the evidence as possible - including that of Mr Blair - in public.
On Monday it was revealed that Mr Blair's former spin doctor Alastair Campbell is to appear before the Inquiry next week. The former No 10 communications director will give evidence on January 12.
Mr Campbell is likely to face questions about his role in compiling the Government's notorious dossier on Iraq's alleged weapons of mass destruction.
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As one of Mr Blair's closest advisers throughout that period, he is also likely to be asked more generally about the Government's attitude in the build-up to war.
