Desires for revenge against the 9/11 perpetrators heightened U.S. public support for war against Iraq in January 2002, controlling for left-right ideology, the rally-round-the-flag effect, and the perceived terrorist threat. Four explanations could account for these findings: prior enemy images of Saddam heightening suspicions of Iraqi complicity in the attacks, as well as anger's tendency to heighten indiscriminate blame, prejudice, and self-confidence. We test for the prejudice effect and find evidence that vengeance heightened support for attacking Iraq in part by increasing anti-Arab prejudice. Vengefulness also partly mediated the effects of retributiveness (proxied by right-wing authoritarianism) on support for war, and largely mediated the effects of patriotism (as intergroup emotion theory would predict). Additional data shows that even as war approached, most supporters acknowledged it would satisfy a desire to avenge 9/11.