The German Marshall Fund of the United States – France (GMF) and the French Institute for International Relations (IFRI) have partnered to launch a joint research program on the transformations of U.S. leadership by the year 2020. This project, which will include the publication of eight articles, seeks to analyze and anticipate the emerging and future changes in U.S. foreign policy in the context of a rapidly changing and increasingly complex and uncertain international environment. The paper series will bring together French, European, and U.S. researchers and experts to explore the factors, both foreign and domestic, that will impact the way the United States will be able to exercise global leadership in the years to come. This brief introduces the series.