Reassurance is likely to play a major role in NATO's new Strategic Concept for three reasons. First, it lies at the core of what the Alliance is all about. While Europe today is more peaceful than at any time in recent memory and an overwhelming threat of the kind we knew in the Cold War is absent, uncertainty and risks lie beyond Alliance borders, trends that could escalate into instability and conflict. History, nationalism, and geopolitical competition have not disappeared from Europe's periphery or world politics.