The Colloquium on Law and Security explores a broad array of emerging issues in the rapidly changing field of national security. The aim of the seminar, therefore, is to define and debate the new, complex and evolving threat environment facing the country in the third decade of the twenty-first century. We will look abroad, including at deteriorating relations with an increasingly powerful China and a belligerent Russia, the threat of cyber warfare and “gray zone” tactics, the weakening of America’s traditional alliances and values, and emerging conflicts in regions such as the Middle East. Each week we will engage with a presentation by an eminent national security expert—including former government officials, legal academics, international relations specialists, journalists, and human rights advocates—as we explore the defining features and dilemmas of today’s national security law and policy.