What led two mortal enemies to become allies nine years after the end of World War II? When the Allies began their occupation of defeated Axis countries, many people favored a program of harsh reparation and demilitarization. For the United States, this was tempered with a desire not only to prevent such a war from happening again but to help the occupied countries rebuild their economic and political infrastructure. This aspiration, coupled with the rise of communist China and its perceived threat not only to Southeast Asia but the world, formed the catalyst for a U.S.-Japanese alliance. The alliance between the United States and Japan persists in spite of changing political world views. The changes which have affected world politics have often resulted in corresponding adjustments to the U.S.-Japan security agreement. From 1954 to the present day, this volume takes an in-depth look at the fundamental nature of the relationship. The book addresses the historical origins of security relations in both countries and the ways in which these formed the basis for their postwar security cooperation and examines the negotiated set of shared military, economic and political agreements and expectations which have shaped their relationship. The work's main focus, however, is the way in which this alliance has evolved. Four cases of significant policy change--in 1960, 1981, 1987 and 1997--are analyzed along with a discussion of the relevant strategic and tactical realities of the time. The reactions of the United States and Japan to recent events such as Iraq's Kuwait invasion and the 2001 terrorist attacks on America are also discussed. Numerous tables are included.