Both U.S. and Japanese policymakers understand that leveraging military resources during a disaster is an opportunity to save lives and property, to help maintain stability and prosperity in affected nations, and to promote the allies' diplomatic interests. However, it must be done carefully to maximize efficiency and avoid undermining humanitarian principles. Together with a handful of other key countries, the United States and Japan can form a valuable crisis core group that cooperates in support of large-scale, UN-led disaster relief operations, but effective civil-military coordination is...