Iraq and weapons of mass destruction
Under the government of Saddam Hussein, the Iraqi government always had an interest in weapons of mass destruction and in long-range guided missiles. Some of the interest was to gain prestige and some was as a deterrent to regional and international powers. It was rumored, but never clear, if Iraq might provide WMD to terrorists.
Early WMD programs
With funding from oil revenues, Iraq, in the 1960s and 1970s, adopted a policy of extending its regional power. Instability in Iran, in the late 1970s, accelerated its armament priorities.
In May 1977, Israeli intelligence determined that the nuclear complex at al-Tuwaitha was growing rapidly and that the reactor facility might soon be ready. The government debated a preemptive military attack. "In the meantime, the Mossad would take steps to buy additional time. These steps included allegedly sabotaging the reactor cores for Osirak before the French could deliver them, as well as assassinating Iraqi nuclear officials. At the same time, the IAF began contingency planning for a strike on Osirak...In October 1980, the Mossad reported to Begin that the Osirak reactor would be fueled and operational by June 1981." The Osirak reactor was attacked on June 7, 1981, setting the Iraqi nuclear program back at least five years, and making chemical weapons a more viable alternative against Iraq.
In 1974, it started a chemical weapons program.  It was by Saddam Hussayn's son-in-law Hussayn Kamil, and initially produced 60 tons of sulfur mustard per year, at first having to import the precursor, thiodiglycol. Eventually, according to Carus, Iraq became self-sufficient in thiodiglycol.
With West German assistance, it also built pilot plants for nerve agents, beginning with Tabun, in the early 1980s.
Both sides used chemical weapons in the Iran-Iraq War.
In 1988, Saddam used lethal chemicals on a mixture of Kurdish insurgents and Iranian troops at Halabja; most of the thousands of casualties were civilians.
Iraq had, but did not use operationally, chemical weapons during the 1991 Gulf War. Their presence was provisionally detected by U.S. Army engineers destroying a munitions dump at Khamisiyah in March 1999; UNSCOM confirmed both weapons and residues. 
The United Nations Special Commission (UNSCOM) was set up to implement the non-nuclear provisions of United Nations Security Council resolution of 3 April 1991, which called for the elimination of weapons of mass destruction and long-range surface-to-surface missiles, as well as manufacturing capability, under Iraq under the rule of Saddam Hussein. UNSCOM was to work with the International Atomic Energy Agency in inspection and enforcement of the nuclear aspects of WMD, and operate directly in chemical, biological, radiological and missile areas.
United Nations Security Council Resolution 687 called for the destruction of Iraqi WMD and long-range missiles. Speaking with FBI agents after his capture, Saddam Hussein said that Iraq had erred by destroying some WMD without UN supervision, 
The continued belief that Iraq was pursuing nuclear weapons led the Bush administration to increase diplomatic pressure on the Iraqi regime. During a speech before the General Assembly of the United Nations on September 12, 2002, President Bush outlined a long list of complaints against the Iraqi government. This included active support and harboring of terrorists (among them members of al Qaeda who had fled from Afghanistan after the US invaded that country), continued development of prohibited missiles, diverting funds from the UN “Oil for Food” program to purchase weapons, and violation of several UN resolutions by refusing to be open about its WMD arsenal. On November 8, 2002, the United Nations Security Council unanimously passed resolution 1441 which declared Iraq in material breach of the 1991 ceasefire agreement and demanded Iraq fully comply with its disarmament obligations. As a result, Iraq agreed to let UNMOVIC weapons inspectors, headed by Hans Blix, back into the country.
Not all military and intelligence believed that Iraq had an active program, such as former U.S. Middle East military commander GEN Anthony Zinni.
In my time at CENTCOM, I watched the intelligence, and never - not once - did it say, “He has WMD.”...Now, I’d be the first to say we had to assume he had WMD left over that wasn’t accounted for: artillery rounds, chemical rounds, a SCUD missile or two. But these things, over time, degrade. These things did not present operational or strategic level threats at best. Plus, we were watching Saddam with an army that had caved in. It was nothing like the Gulf War army. It was a shell of its former self. We knew we could go through it quickly. We’d stripped away his air defenses. He was at our mercy. We had air superiority before we even—or actually air supremacy before we would even start an operation. So to say that this threat was imminent or grave and gathering, seemed like a great exaggeration to me.
On September 4, 2002, George W. Bush called a meeting of eighteen senior U.S. legislators, where they were give a letter saying, in part, "The decision is how to disarm an outlaw regime that continues to possess and develop weapons of mass destruction."
While Saddam, in spite of declarations of disarmament, hinted at nuclear programs, suspicion focused on two areas of possible Iraqi purchasing
- Lightly processed uranium ore ("yellowcake" uranium oxide)
- Strong, light and precisely machined aluminium tubes that might become part of isotopic enrichment centrifuges
Initial reports of uranium tubes
In 2001, Joe Turner, an analyst at the CIA received intercepted faxes showing Iraq was trying to buy 60,000 aluminium tubes from Hong Kong. He concluded they were intended for use as centrifuge rotors; it was reported to the President, and then circulated to top officials on April 10. 
Reviewers at the Department of Energy, however, concluded these were probably not for centrifuge use. They were half the size known to have been tested by Iraq, only barely large enough for a centrifuge. About a month later, the tubes were correlated, by the Army's National Ground Intelligence Center, with similar parts used in Iraqi unguided rockets. 
Iraq had not been buying the tubes secretly, even advertising for them, an argument that they were not intended for a classified program.
Jordanian intelligence intercepted one shipment, which was viewed by then clandestine CIA officer Valerie Plame Wilson. The tubes were piled in a storage yard and exposed to weather, not the handling that would be expected for critical centrifuge applications.
The Niger Uranium Forgeries
In February 2002, as a result of the discovery of classified documents initially revealed by Italian intelligence in October 2001, the Pentagon sent Marine General Carlton Fulford, Jr. to Niger to investigate the claim that Iraq was attempting to buy uranium to revamp its nuclear WMD program. That same month, the CIA sent former Ambassador Joseph Wilson IV to Niger in February 2002. General Fulford and Ambassador Wilson interviewed several high-ranking Niger government officials. Neither found any evidence for the sale; Mr. Wilson concluded that the claim was “unequivocally wrong.”
There was disagreement about the findings of Mr. Wilson’s report within the intelligence community. CIA analysts believed the report confirmed reports about an Iraq-Niger uranium deal, partly because Mr. Wilson’s report included a comment that an Iraqi envoy had visited the African country in 1999. However, State Department analysts decided that Niger would be unwilling or incapable of supplying Iraq with any uranium.
As a result of these conflicting intelligence analyses, the Bush administration remained suspicious and continued to work from the assumption that Saddam Hussein was actively trying to acquire a nuclear weapon. Because of internal disorganization, the CIA failed to obtain copies of the original classified documents, after they were finally made available to American intelligence in October 2002, and ignored warnings from State Department analysts about problems with the documents. The CIA also failed to check the president’s 2003 State of the Union for factual errors. Consequently, the address included the infamous “sixteen words” that “the British government has learned that Saddam Hussein recently sought significant quantities of uranium from Africa.” 
It was not until March 2003 that the International Atomic Energy Agency (IAEA) revealed with conclusive proof that the documents at the basis of the allegations were forgeries. However, the British government claimed it had evidence to the same effect independent of these documents, but had promised the source not to reveal its identity.
Statements by senior officials
Cheney, on September 8, 2002, referred to a New York times story about Saddam's attempts to buy thousands of aluminium tubes, as well as other WMD components. 
On the 9th, George W. Bush, at Camp David, made a similar claim, in the presence of British Prime Minister Tony Blair.
The key evidence of an active Iraqi biological weapon (BW) program came from an Iraqi defector code-named CURVEBALL, run by the German intelligence service, the BND. CIA personnel had never talked to him. CBS News obtained early 1993 video of CURVEBALL, whom they named as Rafid Ahmed Alwa. According to both CBS and Isikoff & Korn, when Tyler Drumheller, chief of the European Division of the CIA Directorate of Operations, was urged to gain access to CURVEBALL, he met with the Washington station chief of the BND in September 2002. That official said it would be a waste of time; the Germans did not trust CURVEBALL, saying "we think he's had a nervous breakdown; we think he's a fabricator." Bob Simon of CBS said Drumheller said "If they had not had Curve Ball they would have probably found something else. 'Cause there was a great determination to do it. But going to war in Iraq, under the circumstances we did, Curve Ball was the absolutely essential case."
A heavily redacted 2004 report from the Senate Select Committee on Intelligence still leaves enough uncensored material to indicate CURVEBALL was not universally accepted. 
Saddam unquestionably played a game of brinkmanship, giving the impression that he had chemical weapons, and the advancing forces in the Iraq War expected them to be used at any time. Nevertheless, postwar inspection did not find any actual stockpiles or production facilities.
- Javed Ali (Spring 2001), "Chemical Weapons and the Iran-Iraq War: a Study of Noncompliance", Nonproliferation Review, p. 45
- Whitney Raas and Austin Long (pril 2006), “Osirak Redux? Assessing Israeli Capabilities to Destroy Iranian Nuclear Facilities”, Security Studies Program, Massachusetts Institute of Technology Working Paper
- W. Seth Carus (July 1989), The Genie Unleashed: Iraq's Chemical and Biological Weapons Production, Washington Institute for Near East Policy, Policy paper No. 14
- Gordon M. Burck and Charles C. Flowerree (1991), International Handbook on Chemical Weapons Proliferation, Greenwood Press, at 32
- Andrew Rathmell, "Iran's Weapons of Mass Destruction," Jane's Intelligence Review, Special Report No. 6, June 1995, p. 15.
- Anthony Cordesman, "Creating Weapons of Mass Destruction," Armed Forces Journal International 126 (February 1989), p. 56.
- Albert J. Mauroni (August, 2001), "Reflections on Khamisiyah - chemical weapons in the Gulf War", CML Army Chemical Review
- Joyce Battle, Brendan McQuade, ed., Interview Session 4, February 13, 2004, Saddam Hussein Talks to the FBI: Twenty Interviews and Five Conversations with "High Value Detainee # 1" in 2004, vol. George Washington University National Security Archive Electronic Briefing Book No. 279
- President George W. Bush’s 2002 Address to the UN General Assembly, United Nations, General Assembly 57, Meeting 2. Verbatim Report. Retrieved May 9, 2008.
- United Nations Security Council Resolution 1441, posted at CNN.com, November 8, 2002. Retrieved May 9, 2008.
- "Transcript, April 2, 2006: John McCain, Tony Zinni", Meet the Press, NBC News, April 2, 2006
- Michael Isikoff, David Corn (2006), HUBRIS: the Inside Story of Spin, Scandal and the Selling of the Iraq War, Crown/Random house, ISBN 0307346811, pp. 21-22}}
- Isikoff and Corn, pp. 37-41
- Commission on the Intelligence Capabilities of the United States Regarding Weapons of Mass Destruction (March 31, 2005), Report to the President of the United States, p. 57
- Report on the U.S. Intelligence Community's Prewar Intelligence Assessments on Iraq United States Senate, ordered July 7, 2004. Chapter 2-b. Retrieved May 8, 2008.
- Report on the U.S. Intelligence Community's Prewar Intelligence Assessments on Iraq United States Senate, ordered July 7, 2004. Chapter 2-k. Conclusion 13. Retrieved May 9, 2008.
- 2003 State of the Union Address, President George W. Bush, January 28, 2003. Retrieved May 8, 2008.
- Senate Intelligence Committee Report (see previous note), Chapter 2-k. Conclusions 18-19, 21.
- Transcript of ElBaradei's U.N. presentation, posted at CNN. March 7, 2003. Retrieved May 8, 2008.
- Michael Gordon, Judith Miller (September 8, 2002), "Threats and Responses: The Iraqis; U.S. Says Hussein Intensifies Quest for A-Bomb Parts", New York Times
- "Faulty Intel Source "Curve Ball" Revealed; 60 Minutes: Iraqi's Fabricated Story Of Biological Weapons Aided U.S. Arguments For Invasion", 60 Minutes, CBS News, November 4, 2007
- Isikoff & Corn, pp. 129-132
- , Report on the U.S. Intelligence Community's Prewar Intelligence Assessments of Iraq, The Record on CURVEBALL: Declassified Documents and Key Participants Show the Importance of Phony Intelligence in the Origins of the Iraq War, George Washington University National Security Archive Electronic Briefing Book No. 234, July 7, 2004, pp. 152-156