Foreign policy alignment in asymmetric alliances

Major powers often form military alliances with much weaker partners. Scholars generally believe that these relationships allow major powers to advance their global policy priorities by securing policy alignment from their partners. However, we know little about how successful major powers are in achieving this goal, largely because measuring foreign policy alignment in asymmetric alliances has proven challenging. Major powers pursue alignment on a wide range of policy dimensions, and the degree of alignment provided by allies varies over time. To address these challenges, we develop a measurement model to estimate the policy alignment of US allies in the post-WWII period. Our approach produces a continuous measure of alignment with US foreign policy priorities for all states from 1950 to 2010. The resulting estimates indicate that allies tend to be more closely aligned with the US than non-allies, while also exhibiting substantial variation across alliances and allies over time. We also use the measure to examine the effect of US alliance commitments on alignment relative to other forms of US support, finding that the US alliance network plays a central role in shaping alignment. These findings provide new insights into the US alliance system and highlight the ability of major powers to advance their global policy priorities through alliance commitments to weaker states.