Dilemmas of Internationalism is a new political history of the 1940s which charts and analyses the efforts of private internationalists to define US internationalism and promote the establishment of the United Nations. Internationalists hoped that the United States would shake off the fear of entangling alliances that had characterised the nation's history, replacing isolationism and unilateralism with a new, involved and multilateral approach to foreign affairs. During and after World War II, a number of private individuals and organisations were at the forefront of the fight to change the nature of US foreign policy. This book focuses in particular on the most important internationalist organisation: the American Association for the United Nations (AAUN), known as the League of Nations Association through 1944. It situates the AAUN in the vast network of private organisations promoting an internationalist foreign policy during and after World War II, and analyses the connections between the AAUN and the US government and key public figures who proposed a more internationalist foreign policy. One of the most innovative aspects of Dilemmas of Internationalism is its focus on state-private interaction with regard to defining internationalism. Most previous works on wartime internationalism neglect considerations of state-private interaction, or fail to significantly develop them. The study also acts as a corrective to the general neglect of state-private interaction during this period, turning attention away from the common focus on the Cold War to the crucial phase during and immediately after World War II. Beginning with the US entry into the War, this study continues through the onset of the Cold War to early 1948, ending with the passing of the Marshall Plan. By 1948, the path of US internationalism appeared firmly fixed by a Cold War framework, but in 1941, US entry into the Second World War offered the opportunity to develop a more multilateral approach to foreign affairs, and create a more just and peaceful world. This book is a much-needed history of the attempt to seize that opportunity.