序論　政権交代と外交

Changes of government parties had been regarded as unrealistic in the post-war Japan. As the party system has been transformed during the 1990s, however, changes of government parties have been realized. Moreover, the result of elections was partially due to the government’s diplomatic performance. That is why this topic has received much more attention. We extend the research scope by including not only changes of cabinets by the same government party but also regime changes such as breakdown of democracy or democratic transition. We often ascertain that changes of leaders in the same party sometimes brought much more different policies, but regime changes brought very little change on their policies.<br> Regarding the impact of governmental performance on changes of governments, we must accumulate many case studies. “Failure” of diplomacy is sometimes regarded as fatal and promotes changes of governments, but ordinary governments usually never regard it as failure. How much weight is the evaluation of diplomatic performance considered in the voting behavior in elections? How much change do electoral results bring in terms of political arrangements? Domestic political process is important for explaining the impacts of international factors on changes of governments.<br> Moreover, we must take the impact of governmental changes on the continuity of diplomacy into consideration. On the one hand, diplomacy might have to be consistent regardless of governmental changes because its national interest is relatively constant according to its international environment, and its reliable relation with other countries is so important lest the revolving policy changes should cause damage to its diplomacy. On the other hand, changes of foreign policy due to governmental changes should be taken for granted because diplomacy has to be under democratic control. What is problem is how to compromise the mutual different views of previous diplomatic achievements between countries.<br> The role of political leaders is important in terms of diplomacy, but changes of leaders never always bring policy changes. Moreover, the role of such professional institutions as NSC is also important for diplomatic stability, but they cannot automatically guarantee diplomatic continuity. The institutionalization of decision-making process is also important, but performance of leaders are sometimes beyond institutional constraints. International constraints are regarded as decisive for guaranteeing diplomatic continuity. What is important is not whether such constraints exist or not, but how much constraint governments perceive. A government ordinarily cannot but obey the constraints, but it sometimes tries taking advantage for promoting policy changes. Nixon’s policy toward Vietnam and Brandt’s Ostpolitik are regarded as latter cases. International constraints are not always obstructive for policy changes, and the new government sometimes can change the perception toward constraints and take the chance for policy changes.