Chilcot inquiry: Iraq war investigation explained

The Chilcot inquiry, chaired by Sir John Chilcot, will cover Britain's involvement in Iraq between summer 2001 and 2009, when the army ended combat operations in the country. This will include the run-up to the conflict, the military action and its aftermath.

The inquiry, which takes place in the Queen Elizabeth II conference centre in Westminster, will attempt to identify what decisions were made, how they were taken, and what lessons can be learned. Proceedings will mostly be open to the public and the press, though certain information deemed as likely to harm "the public interest, national security, defence interests or international relations" will be heard behind closed doors.

Who is expected to appear?The inquiry will begin by asking senior figures from the intelligence services, the Foreign Office and the military about preparations. The big hitters, including Tony Blair, Gordon Brown, Jack Straw and possibly former attorney general Lord Goldsmith, are expected to be called before the panel in either January or February next year.

Who is Chilcot?Sir John Chilcot is a retired, 70-year-old career civil servant whose most senior post was as Permanent Under-Secretary of State at the Northern Ireland office. He has also served as a Private Secretary to three Home Secretaries: Roy Jenkins, Merlyn Rees, and Willie Whitelaw.

Who else is on the five-member committee?• Sir Lawrence Freedman, a Professor of War Studies at King's College London, whose books include Kennedy's Wars: Berlin, Cuba, Laos and Vietnam, and the Official History of the Falklands Campaign.

• Sir Martin Gilbert, a biographer of Winston Churchill, who has accompanied both John Major and Gordon Brown on trips to the Middle East.

• Sir Roderic Lyne, a deputy chairman at Chatham House think tank, who spent over 30 years working for the Foreign Office, and ended his career there as British Ambassador in Moscow.

• Baroness Usha Prashar, a crossbencher in the House of Lords, who works as the Chairman of the Judicial Appointments Commission.

What are the criticisms?The choice of Chilcot as the inquiry's chairman has been questioned. He is seen by some as too deeply rooted in the Whitehall establishment, and lacking the backbone to be firm with senior government figures.

When he asked questions during the Butler inquiry, which looked into the failures of the intelligence services before the Iraq war, Chilcot was criticised for not being aggressive enough in his cross-examination.

Philippe Sands, an international lawyer, said that some of his questions to Lord Goldsmith, the attorney-general, were 'spoonfed' and gave "every impression of being designed to elicit a response from the attorney general that would demonstrate the reasonableness of his actions and those of the government".

There are also worries about the make-up of the panel, not least because its members were personally chosen by Prime Minister Gordon Brown, and none of them ever publicly criticised the war. It contains no judges or QCs, which has led some to doubt whether its members have the necessary cross-examination techniques and forensic legal questioning skills to determine the legality of the invasion.

There are also questions over whether the committee has a sufficiently broad and relevant range of expertise. It contains two historians, but nobody from the military, or with aid and reconstruction experience. Another concern is that witnesses will not be obliged to speak under oath.

What questions need to be answered?The inquiry will examine how Tony Blair became convinced that the UK needed to go to war, and will ask what assurances he gave George W Bush about UK support for military action in Iraq when he visited the president's ranch in Crawford, Texas, in April 2002.

Sir Christopher Meyer, the British ambassador in Washington at the time of the invasion, will be asked about the discussions which took place between the President and the Prime Minister. As in the Butler inquiry, the extent to which the intelligence was molded to fit the mission will be raised.

Related to this is the question of how much the government delayed military preparations for political and diplomatic reasons. Military top brass complained that there was a lack of equipment, including body armour.

There will also be questions asked about what caused Lord Goldsmith, the attorney general, to change his mind about the legality of the war. Perhaps most importantly though, Chilcot and his team will want to find out why Iraq descended into civil strife after Saddam was removed from power. Senior figures at the Cabinet Office warned ministers in July 2002 that a "postwar occupation of Iraq could lead to a protracted and costly nation-building exercise". Was this advice ignored?

How long will the inquiry take?The inquiry will take a break in the run-up to the general election campaign, and the findings are not expected until late 2010, or even as late as early 2011. ·