NATO was formed in 1949 to defend Western democracies from an aggressive Soviet Union. With the collapse of European communism four decades later, it fulfilled its purpose. Since then, NATO has managed to remain useful: its roster has nearly doubled and it played a positive role in advancing democratic governance in the new member states. Moreover, it has been fighting to plant democracy in Afghanistan, trying to save its prospects in Bosnia and Kosovo, and has provided disaster relief around the globe. NATO’s challenge now is to decide whether it should become a global alliance for democracies or stick to its core area; what level of operational ambition it should pursue; and how to convince its members to meet their commitments.