In this article, the author describes and analyzes the transformation of Japan, from the perspective of Asia Pacific historical configuration and the international relations theory. The transformation of Japan goes from a country subordinated to the Chinese and European empires, to a modern nation, a military and economical powerful country in the economics and geopolitics of XIX and XX century settings, particularly in the 1900-1980 period. The article describes the way in which the transformation took place, as well as the human, nature, technological and financial costs that Japan had to paid in arriving where it is now. However, these costs were not just for Japan, but for most of the countries of the Asia Pacific region. In this transition from subordinated to imperial country, from the end of the XIX century and at the beginning of the XX, to a modern country, in the second half of the XX century, Japan waged wars against its neighbor countries, like China and Russia, as well as invasions to other countries and territories, and participated in two World Wars. Finally, the article concludes that some elements such as Japan's importance in Asia Pacific region, its international policy, its imperial voracity, its new American subordination since the middle of the XX century and its new international linking strategy through economic cooperation agreements, were the prelude of a new stage in Japanese historical construction into the XXI century. [ABSTRACT FROM AUTHOR]