The objectives of the U.S. government’s European Phased Adaptive Approach (EPAA)-the U.S. contribution to NATO missile defense-set out by President Barack Obama in September 2009 were modified over the course of his administration, which ended in January 2017. This thesis explores how U.S. interactions with Russia and the NATO Allies influenced the decisions on modifications made by the United States-for example, the cancellation in March 2013 of the EPAA’s projected fourth phase. The thesis finds that U.S. interactions with the NATO Allies and Russia played a role in revisions in the original objectives of the EPAA but were not the only contributing factors. Budgetary constraints, technological issues, and reassessments of threats also led to modifications in the EPAA program. Providing for the defense of populations, national territories, and forces remains a high priority for the United States and its NATO Allies, and the Alliance has repeatedly sought dialogue and cooperation with Russia concerning missile defense. Events have vindicated the EPAA’s design for adaptability to benefit from technological innovations and to meet the evolving needs for Alliance protection in the international security environment.

Subjects: European Phased Adaptive Approach (EPAA); NATO missile defense; Alliance missile defense; Russia; NATO; United States (U.S.); ballistic missiles