What was it that eventually put a period to the Anglo-Japanese alliance at the beginning of the interwar years, a treaty that had been the most successful treaty in East Asia to that moment, through two victories in the Russo-Japanese War of 1904-1905 and the First World War of 1914–1918? As many previous works have claimed, was the strong pressure from the United States decisive in terminating the alliance? Or else,as some British works in relatively recent years have argued, was the opposition of the United States no more than the last push to bring down the curtain on the arrangement, if discarding the alliance had already become all but a foregone course in London by the time Washington made clear its opposition?
This study will challenge both accounts. First, it will show that the American opposition alone was not and could have not been enough to put an end to the alliance, even though this opposition did indeed create the international dispute itself over whether or not the alliance should be continued. At the same time, the study will deny that London was almost independently decided on the matter. The British government did need something external to help it with its decision; however, that was not the increase of American pressure but the restoration of the credibility of America’s commitment to a new international order-building program, at least in the Asia-Pacific region. To this point, American diplomacy had had trouble displaying this commitment, due to the country’s failure to join the League of Nations that the US itself had conceived.
Therefore, secondly, this work will emphasize the serious dilemma that the British alone confronted in the international politics that led to the lapse of the alliance. That dilemma can be well understood as a variety of the “security dilemma in alliance politics” very well known to IR students. Major previous works,especially in British research, believe that Japan consistently held the alliance to be more significant than Britain did until the last day of the treaty, because the former gained greater advantages through an alliance with the leading power in world politics. However, this study will largely revise this view by describing both Britain’s international political dilemma and Japan’s diplomatic changeover in the aftermath of the Great War.