Contributor(s): Professor Matthew Connelly | The interwar years are vital to understanding the rise of the U.S. national security state and the government’s approach to official secrecy. World War I both revealed the dangers of secret diplomacy to the world, and rationalised its necessity to its leaders. The ensuing period was marked by intense struggles over the limits to official secrecy. Woodrow Wilson both advocated for the prosecution of anyone who revealed national defense information, but also called for open covenants between nations, openly arrived at. For Wilson, if the US did not join the League of Nations it would remain a nation in arms with a vast intelligence-gathering apparatus, forced to curtail civil liberties. It was not until World War II that Wilson’s premonition finally came into being. Professor Matthew Connelly is Philippe Roman Chair in History and International Affairs at LSE IDEAS for 2014-2015. Currently a professor in the Department of History at Columbia University, Matthew Connelly is also founder and director or the LSE-Columbia University Double Degree in International and World History. His current research focuses on planning and predictions, and using data science to analyse patterns in official secrecy. He received his B.A. from Columbia and his Ph.D. from Yale He has authored a wide-range of articles and publications, including the award-winning Diplomatic Revolution: Algeria’s fight for independence and the origins of the post-Cold War era, which has won five prizes since its publication. His most recent book, Fatal Misconception: the struggle to control world population, was chosen as one of the best books of the year by The Economist and the Financial Times. Professor Arne Westad (@OAWestad) is the director of LSE IDEAS. LSE IDEAS (@lseideas) is a centre for the study of international affairs, diplomacy and grand strategy. Credits: Tom Sturdy (Audio Post-Production), LSE AV Services (Audio Recording).