Abstract: The international relations in the first half of 20th century in East Asia is characterized as a process of transformation from joint control of major powers to amonopoly by Japan which remains a major player in the arena of the international relations of the region.The source of major conflict in this period manifests itself as incessant aggressions of Japan against China.In spite of keeping the stability of the region under the Washington System for a limited period,Japan upsets the stability by initiating a series of aggressive wars and concocts a "Great Asian Co-Prosperity Sphere" based on its policy objective of establishing and cementing an East Asian New Order with Japan at the helm.But the aggressive and expansionist policies of Japan meet with strong and unified opposition from China and the international society and end up with abject failure eventually.