This thesis focuses on the following questions: What accounts for U.S. foreign policy? Where is causation located in the foreign process? What changes have taken place in this process over the past 20 years and what are its present characteristics? In providing answers to these questions I refer to James Rosenau's pretheory, a widely employed theoretical framework for the analysis of foreign policy. Rosenau identified five interrelated variable categories which together determine the foreign policy behavior of the United States. He assigned relative potencies to the variable categories thereby ranking them according to their explanatory power. In this thesis, an adapted version of Rosenau's pretheory was used for the analysis of the first major foreign policy crisis of the Reagan administration, the Soviet pipeline sanctions. This foreign policy episode proved to be an excellent illustration of how changes in the domestic and external environment have caused a transformation of U.S. foreign policy in the past two decades. It was found that the domestic foundation of U.S. foreign policy - congressional bipartisanship, executive branch unity, a supportive public and the backing of interest groups - has been replaced by a divided public, antagonist interest groups, a fragmented Executive, and an assertive Congress. These domestic changes were accompanied by external changes, especially the declining ability of the United States to control its external environment. These factors placed constraints on an independent U.S. foreign policy and most of them proved to promote continuity rather than change in the foreign policy behavior of the United States. / Master of Arts

This paper surveys U.S. foreign policy in the late 1970s and early 1980s as the American administration reacted to the Soviet Union's interventions in Afghanistan and Poland and to its planned gas pipeline to Western Europe. Chapter I outlines the origins of the pipeline project; Chapters II and III describe U.S. foreign policy toward the Soviets during the Carter and Reagan administrations. Chapter IV focuses on the economic sanctions imposed against the Soviet Union by the United States and their failure to block or delay the pipeline, and Chapter V stresses the inability of economic sanctions-- in this and other instances--to achieve political ends.