The US invasion against Iraq has been regarded as a turning point in the foreign policy of the United States as well as a salient event in international politics. It is argued that the invasion represents a shift in American foreign policy from a hegemonic to an imperial one. Although the US policy shift faced significant negative reactions all around the world, it was, at least for a while, celebrated inside the United States. The important question here is about the way in which such a shift became possible in US foreign policy making. This article discusses the constitution of this policy ithin an appropriate discursive context inside American polity as well as the US public. The main argument here is that the successful articulation of a few discourses provided the context for the possibility of such a shift. Liberalism, exceptionalism, and national security as the basic discourses constituting US identity and interests included elements the articulation of which could legitimize the change in foreign policy. What made Iraq as a ‘legitimate’ target of the new foreign policy was a securitization discourse that represented it as a rogue dangerous actor in world politics that would directly threaten the United States. It is concluded that despite the realization of the new foreign policy there are other discourses and sub-discourses in the US that may pave the way for resistance against its persistence