The Obama administration's decision to reconfigure its missile defense plans in Europe will have significant implications for Turkey and its alliance relationships. The new architecture will align more closely with near-term risks from Iran and elsewhere, and will offer improved defenses and strategic reassurance to NATO's southern allies, above all, Turkey. To capture the benefits of this shift, the United States and NATO need to explore the possibility of basing some elements of the new system in Turkey. With NATO, Turkey can also play a leading role in new missile and air defense initiatives in the eastern Mediterranean. All of this will cast a spotlight on Turkey's policy toward Iran's nuclear ambitions, and looming decisions on sanctions and the possible use of force.