The purpose of this article is to reevaluate five hypotheses that have been proposed regarding the question of “why the US invaded Iraq.”

It remains, and will continue to be, important to address this question today. First, the Iraq War has had significant consequences for the US, the Middle East, and the world as a whole since its inception. Understanding the motivations behind the initiation of this war is therefore an essential task in gaining insights into today’s international security environment. Second, the war has also raised important questions about the decision-making processes that led the major powers to engage in conflict. As evident from the case of Russia’s invasion of Ukraine, which commenced in January 2022, these issues are still under debate, and an examination of the reasons for the onset of the Iraq War can further enrich such discussions.

The five hypotheses that have been proposed in prior research regarding the causes of the Iraq War are generally as follows (with some overlapping points): (1) the WMD hypothesis, (2) the petrodollar hypothesis, (3) the Israel lobby hypothesis, (4) the neo-con hypothesis, and (5) the performative war hypothesis. How valid are any of these hypotheses?

The conclusions drawn in this paper are as follows. First, the Israel lobby and neo-con hypotheses, which have often been discussed in the past, are, in fact, relatively weakly supported. Israeli security concerns were a minor factor in initiating the Iraq War, and neoconservative ideals were never adopted as fundamental policies by the Bush administration. Figures like Wolfowitz and other neo-cons both inside and outside the administration were primarily utilized to garner support for the war within Congress and public opinion. Second, Cheney and Rumsfeld had formulated the concept of the Iraq War prior to the September 11 attacks, rooted in the idea of performative war, or hegemonic realism. The opportunity to execute this concept arose on September 11. Their thinking did not revolve around liberal ideals of democratic expansion, nor did they leave room for a negotiated settlement. Third, Bush, while influenced by senior officials who were actively pushing for war in Iraq, sought a diplomatic solution until the very end. However, following the failure of the final negotiations, he turned to support the war.

It should be noted that, although there is some circumstantial evidence supporting the petrodollar hypothesis, obtaining conclusive evidence or testimony to substantiate it with a high degree of certainty was not possible. Therefore, the validity of this hypothesis must be regarded with caution in this paper, and further research is required.