This book celebrates the continuing importance of a world-class leader in the theory and scientific analysis of international relations and comparative politics. Topics on which Karl Deutsch wrote prolifically included nationalism, social communication, European integration, cybernetics, war & peace, arms control, social cybernetics, general systems analysis, and global modeling. He had a deep understanding of European political and intellectual history, experienced the violence induced by nationalism in pre-WWII Europe, and in 1938 fled Czechoslovakia for the United States following Hitler's takeover of the Sudetenland. Subsequently he pioneered the development and analysis of large-scale political and social data across nations and over time. He became a powerful global proponent of widespread access to this data and its public scientific evaluation. He was a world citizen, and very likely the most distinguished social scientist on international relations of his generation.