The claim that Iraq possessed Weapons of Mass Destruction (WMD) led to the invasion of Iraq in 2003 by the US army. For the George W. Bush administration, the likely presence of WMD in Iraq was the major justification for going to war. However, Bush’ opponents suspected he used the WMD-dispositive as a legitimation for an invasion that was already set in motion for different reasons. The Iraq invasion and the underlying ideas about the presence of WMD thus provide a tangible case for the analysis of theories of conspiracy and security. The development of the WMD-dispositive will be contextualized using the toolkit of securitization theory. The article explores the notions of security and conspiracy that were used to build the dispositive and shows how it ultimately failed and turned into a counter-narrative in which the Bush administration itself became the Great Conspirator.