The loss of life that resulted from the sinking of the fisheries training vessel Ehime Maru by the nuclear submarine USS Greeneville off Hawaii in February 2001 exemplifies the risks to United States–Japan alliance relations posed by US global military deployments. Following a pattern of incidents involving the US military in Japan itself, the collision violated Japanese expectations of benevolence from its stronger partner and put considerable pressure on the government to seek public apology and reassurance. This article examines the interplay of culture, national security interests and domestic politics in framing both perceptions and diplomacy during the crisis. While differences at both the cultural and security levels complicated diplomacy, asymmetry in the respective domestic political stakes, combined with overriding and largely congruent security interests, helped the United States to provide Japan with the requisite reassurance. After a decade of alliance drift, both Japan and the United States were determined to forestall defection by their alliance partner.