This study examines the transatlantic security divide through the strategic culture lens, taking a comparative case study approach. It analyzes the emergent EU strategic culture by looking at the European Security Strategy, European security elite speeches, and ESDP operations. It examines the same evidence to determine the predominant trends in American strategic culture during Operation Iraqi Freedom and finds the greatest divide in the ideational foundation of operations, particularly as concerns perceptions of legitimacy. In the area of multilateralism, there is a greater similarity than is usually argued as concerns ad hoc coalitions of the willing: the EU forms coalitions with non-EU partners, allows individual members to decide whether to contribute troops and thus carry financial obligations or not, and now opens up the possibility for 'structured enhanced cooperation' in ESDP, despite the legitimacy derived from institutionalized cooperation stressed in public. The use of force only as a last resort is upheld by both in public diplomacy; however, in reality both keep all options open of when to act, even though the EU does stress less the use of force and more crisis prevention and non-military tools, while the U.S. intervention in Iraq was instrumentally declared as a last resort.