European Security and Defense Policy (ESDP) has become a contentious subject in transatlantic security relations. This essay identifies the ambiguities that have occurred in the policymaking on both sides of the Atlantic that appear to have generated a basic lack of confidence and trust in the other side's good intentions and commitment to cooperation. It does so by sketching three historical time periods—1981–1986, 1988–1996, and 1998–2004—that convey the recurrent patterns and outcomes in the ESDP dispute. These three cases cover the periods (1) from the London Report on European Political Cooperation to the Single European Act and the Western European Union Security Platform, (2) the Maastricht Negotiations on a Common Foreign and Security Policy, and (3) the evolution of ESDP from St. Malo to Brussels.