Abstract
This research sheds light on the structural causes of Japanese policy responses to regional power transition that have been often ambiguous and contradictory. No doubt, Japan is one of the most important allies for the US in light of its proactive participation in defense burden–sharing activities. This research observes, however, that Tokyo now finds itself facing the dilemma of being pressured to line up behind US policy initiatives that may be deemed contrary to the interests of Japan's national security. According to the “intra-alliance bargaining-based” explanation, the smaller state would then strive to ensure that its advantages can be strengthened and weaknesses mitigated in its multifaceted bargaining portfolio for dealing with its American ally to defend and uphold its national interests, not just through the alliance, but within the alliance itself. This would require the junior ally to invest in enhancing the credibility of its threat of exit via alternative options in order to manufacture bargaining power, thereby accounting for the case in which Japanese policy responses to regional power transition have become ambiguous and contradictory.