The significant characteristic of the Treaty of Lausanne, with its comprehensive structure of the vast areas of issues included, consists in the wide coverage of regions on the globe represented by its party states: Europe, Near East, and Far East, according to the terminology at that time. In the history of the world and international law, ‘encounter’ is a critical element. West meets East, or East meets West. From this perspective, touching upon the role of Japan, this chapter will examine the role of great powers based upon the universal values of the globe for solidly building peace and order. This past experience of the treaty applies itself to the future endeavor of mankind for the same purpose, too.