The U.S.-Japan alliance originated in cooperation during the Korean War.
Since the Meiji era, the Korean Peninsula has been central to Japan’s security, and after World War II Japan relied on its alliance with the United States for defense.
This article examines the evolution of Japan’s security framework and the challenges posed by North Korea today.

The origin of the U.S.-Japan alliance lies precisely in cooperation between Japan and the United States during the Korean War.
2018-01-10.
The following is from an article by Professor Kazuya Sakamoto of Osaka University published in this month’s issue of the monthly magazine WiLL.
Had I not faced the trials given to me by God, I might have remained at Kyoto University as my high school mentor strictly instructed and pursued a life as an academic.
Professor Sakamoto graduated from the Faculty of Law at Kyoto University and now serves as a professor at Osaka University, the alma mater of my friend.
Reading this article, I felt that this was not mere coincidence.
Regarding the passages before and after his statement, “It is said that China seeks hegemony. However…,” readers will likely think that the correctness of the “hegemonic stability theory,” which marked the beginning of my Turntable of Civilization, has been proven by Professor Sakamoto.
All emphasis in the text except for the headings is mine.
Does China, which seeks hegemony, have any friends.
Leaders who are not chosen by elections must constantly demonstrate the legitimacy of their rule through performance.
The key to security is the Korean Peninsula.
The year 2018 marks the 150th anniversary of the Meiji era.
As it is a fitting milestone, why not take this opportunity to recall the history since the Meiji Restoration and once again consider Japan’s diplomacy and security.
Japan now faces the threat of North Korea’s nuclear and missile development, and for the past 150 years the Korean Peninsula has been a crucial place for Japan’s security.
From the Meiji era until before the war, self-defense for Japan included the security of the Korean Peninsula.
The Sino-Japanese and Russo-Japanese wars were fought to prevent major hostile powers from advancing onto the Korean Peninsula.
The Korean Peninsula is a place shaped like a dagger protruding from the Asian continent toward Japan.
Japan had to protect the peninsula for its own defense, even if it meant dispatching troops.
After the war, however, this was no longer the case.
Postwar Japan, having learned bitter lessons from overseas deployments, became a country that would not, could not, and did not wish to send troops to the Korean Peninsula, even for self-defense.
That may be so, but did the Korean Peninsula cease to have any connection with Japan’s self-defense after the war.
It did not.
So how was Japan to ensure its own defense, including the security of the Korean Peninsula.
It was to be managed through cooperation with the United States, in other words, through the U.S.-Japan alliance.
The origin of the U.S.-Japan alliance lies precisely in cooperation between Japan and the United States during the Korean War.
During this war, Japan entrusted the security of the Korean Peninsula to the actions of the UN forces centered on the United States, while itself devoted to supporting the UN forces by providing bases and other assistance.
In the year after the Korean War armistice (1954), when the Self-Defense Forces were established, the Diet passed a resolution prohibiting overseas deployment, and it is clear that the “overseas” referred to here had the Korean Peninsula in mind.
It was resolved that even if something were to happen again on the Korean Peninsula, the Self-Defense Forces would not be dispatched.
Sixty years later, in 2014, the government revised its constitutional interpretation regarding collective self-defense, and even then Prime Minister Shinzo Abe clearly stated in the Diet that Japan would not exercise collective self-defense on the Korean Peninsula to assist U.S. forces.
The Self-Defense Forces will not be deployed to the Korean Peninsula, but if necessary U.S. forces will be dispatched, and Japan will support those U.S. forces.
This division of roles within the U.S.-Japan alliance is a mechanism by which Japan, unlike before the war, can fulfill its self-defense without going directly to the Korean Peninsula itself.
In recent years this framework has been significantly strengthened through new security legislation and updated guidelines, yet Japan now faces a severe test as to whether it can respond effectively to the current North Korean issue.
To be continued.