优先购买权必然依赖于即将到来的攻击提升知识。高质量的情报是因此重要的优先购买权是有效的，被视为正当的。在历史上的第一次，在伊拉克战争的原因，一个完全基于情报评估。联合评估，首先，伊拉克拥有大规模杀伤性武器的联合国安理会决议违反，其次，伊拉克有国际恐怖主义的联系。这些评估，结合，是联盟试图建立一个公正的原因入侵的基础上自我防御（众议院情报和安全委员会2003，15）的基础上。到伊拉克2003三月入侵之前，美国国务卿Colin Powell提出的安理会旨在表明伊拉克正在大规模杀伤性武器，在违背联合国决议的情报信息。所谓的大规模杀伤性武器解除伊拉克政权的提出为主要目标，和理由，美国领导的对伊拉克的战争。在战争的后果中，联盟的失败，以产生确凿的证据，伊拉克？的大规模杀伤性武器引发激烈的战前政治争论是否要战争是做正确的事（sacrborough 2003，12）。不完美的情报是建立一个公正的事业的基础，但这正是美国及其盟国试图做的。特别是，该联盟主要依靠人类的智慧，主要来自叛逃者。这种智能有时是模糊的，不准确的或以其他方式误导。来源可能是谋求政治议程或取食的目标代表一个情报机构情报。来源可能会提出自己的评估，假设和解释的事实，而这些实际上可能是错误的（阿克曼2006）。当联盟试图建立一个公正的原因入侵伊拉克的基础上自卫，一个根本性的问题，从使用的术语？大规模杀伤性武器？。在入侵前的情报对伊拉克的公开演讲和战争的情况下，清晰度，三类大规模杀伤性武器，融合成一个单一的威胁整个。这样做，尽管之间的巨大差异核科学，生物和化学武器，从而产生不同的安全挑战（埃克乌斯2003）。不断重复？大规模杀伤性武器的威胁？集中在一起的可能性很高，伊拉克拥有化学武器，这些武器本身只构成一个小的威胁，完全缺乏证据表明，它拥有核武器，这将是一个更大的威胁。一个由卡耐基国际和平基金会的报告认为，一月2004，对于核武器和化学武器，对伊拉克构成的威胁程度基本上可知当时联盟决定参战。伊拉克？在1991次海湾战争结束后，联合国武器核查人员已被联合国武器核查人员拆除了。虽然伊拉克有兴趣重新启动一个核计划，但没有证据表明它实际上是这样做的。核设施？不同于化学或生物的？往往是大的，昂贵的，依赖于昂贵的进口，并很难隐藏。1991次战争结束后，联合国武器核查人员发现，伊拉克？化学神经药物失去了大部分的杀伤力，早在1991。关于伊拉克吗？的生物武器的地位，该联盟几乎没有什么可以继续。这并不奇怪，因为这类武器的精确情报本质上是难以获得的。例如，一个生物制剂生产设施可以位于一个城市，几乎没有什么区别的其他建筑物的卫星图像。联合国武器核查在2002-2003年没有透露任何生物制剂或武器在伊拉克的证据，或一个程序来生产（联合国2003）。
Pre-emption necessarily relies on advance knowledge of an impending attack. High quality intelligence is therefore vital for pre-emption to be effective and to be seen as justified. The cause for war in Iraq was, for the first time in history, one based entirely on intelligence assessments. The Coalition assessed, firstly, that Iraq possessed WMD in contravention of UN Security Council resolutions and, secondly, that Iraq had links to international terrorism. These assessments, in combination, were the foundation on which the Coalition sought to construct a Just Cause for invasion based on self defence (House of Commons Intelligence and Security Committee 2003, 15). Prior to the invasion of Iraq in March 2003, US Secretary of State Colin Powell presented the Security Council with intelligence information intended to show that Iraq was running WMD programs in contravention of UN resolutions. Disarming the Iraqi regime of alleged WMD was put forward as the main goal of, and justification for, the US-led attack on Iraq. In the aftermath of the war, the failure of the Coalition to produce conclusive evidence of Iraq?s WMD reignited the fierce pre-war political debate over whether going to war was the right thing to do (Sacrborough 2003, 12). Imperfect intelligence is a shaky foundation on which to build a Just Cause, yet this is precisely what the US and its allies tried to do. In particular, the Coalition relied heavily on human intelligence, derived mainly from defectors. Such intelligence can sometimes be vague, inaccurate or otherwise misleading. Sources might be seeking to advance a political agenda or be feeding an intelligence agency disinformation on behalf of the target. Sources might present their own assessments, suppositions and interpretations as fact, and these may actually be false (Ackerman 2006). When the Coalition sought to establish a Just Cause for invading Iraq based on self-defence, a fundamental problem arose from the use of the term ?weapons of mass destruction?. In the public presentation of pre-invasion intelligence on Iraq and the articulation of the case for war, the three categories of WMD were fused into a single menacing whole. This was done despite the huge scientific differences between nuclear, biological and chemical weapons, which in turn generate different security challenges (Ekeus 2003). Constant repetition of ?the WMD threat? lumped together the high likelihood that Iraq possessed chemical weapons, which themselves constitute only a minor threat, with the complete lack of evidence that it possessed nuclear weapons, which would be a far greater threat. A January 2004 report by the Carnegie Endowment for International Peace argues that, with respect to nuclear and chemical weapons, the extent of the threat posed by Iraq was largely knowable at the time the Coalition decided to go to war. Iraq?s nuclear program had been dismantled by UN weapons inspectors after the 1991 Gulf War. Although Iraq was interested in restarting a nuclear program, there was no evidence that it had actually done so. Nuclear facilities ? unlike chemical or biological ones ? tend to be large, expensive, dependent on expensive imports, and very difficult to hide. After the 1991 war, UN weapons inspectors had found that Iraq?s chemical nerve agents had lost most of their lethality as early as 1991. Regarding Iraq?s biological weapons status, the Coalition had almost nothing to go on. This is not surprising as accurate intelligence about such weapons is inherently difficult to obtain. For example, a biological agent production facility could be located in a city and be virtually indistinguishable from other buildings in a satellite image. UN weapons inspections in 2002-2003 did not reveal evidence of any biological agents or weapons inside Iraq, or of a program to produce them (UNMOVIC 2003).