This chapter examines the US role in Asia in a historical context and explains how it has evolved over the years as a result of the geostrategic changes taking place at regional and international level. As no foreign and defence policy is ever formulated in a vacuum, America’s regional role has been significantly shaped by the ever-changing strategic context and by the way in which American policymakers have perceived political change globally and regionally. It is against this backdrop that the current challenges to US pre-eminence in Asia should also be assessed. With the rise of Chinese economic and military power in the region and with uncertainties surrounding Washington’s ability and resolve to maintain a strong presence in Asia, the future of US power does not seem to be as assured as it was only a decade ago.
Since the end of the Second World War, the United States have played a major role in Asia. Measured against American participation in Asian affairs before 1939, Washington's post-war regional engagement has been nothing short of breathtaking. From limited involvement, the US transformed itself into a major player, if not the major player, on the Asian scene. This chapter seeks, therefore, to chart the development of American diplomacy in Asia since 1945 and explain how the US went about building its web of regional relationships and then maintaining them. Furthermore, it aims briefly to discuss the prospects for these regional relationships. In this context, it provides a broad introduction to those chapters that specifically explore Washington's bilateral relations with the principal regional actors.