The twentieth century is as remarkable for its world wars as it is for its efforts to outlaw war in international and constitutional law and politics. Japan in the World examines some of these efforts through the life and work of Shidehara Kijuro, who was active as diplomat and statesman between 1896 until his death in 1951. Shidehara is seen as a guiding thread running through the first five decades of the twentieth century. Through the 1920s until the beginning of the 1930s, his foreign policy shaped Japan’s place within the community of nations. The positive role Japan played in international relations and the high esteem in which it was held at that time goes largely to his credit. As Prime Minister and man of the hour after the Second World War, he had a hand in shaping the new beginning for post-war Japan, instituting policies that would start his country on a path to peace and prosperity. Accessing previously unpublished archival materials, Schlichtmann examines the work of this pacifist statesman, situating Shidehara within the context of twentieth century statecraft and international politics. While it was an age of devastating total wars that took a vast toll of civilian lives, the politics and diplomatic history between 1899 and 1949 also saw the light of new developments in international and constitutional law to curtail state sovereignty and reach a peaceful order of international affairs. Japan in the World is an essential resource for understanding that nation’s contributions to these world-changing developments.