Based on a paper by Osaka University professor Kazuya Sakamoto, this essay examines how the Korean Peninsula has remained central to Japan’s national security.
From the Sino-Japanese and Russo-Japanese wars to the U.S.–Japan alliance and the North Korea issue, it traces the foundations of Japan’s strategic policy.

The Sino-Japanese and Russo-Japanese wars were fought to prevent massive hostile powers from advancing onto the Korean Peninsula.
January 10, 2018.
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 undergone the trials given to me by God, I would likely have remained at Kyoto University as my high-school mentor had sternly instructed and lived the life of a scholar.
Professor Sakamoto graduated from the Faculty of Law at Kyoto University and now serves as a professor at Osaka University, the alma mater of one of my friends.
Reading this article, I felt it was not merely 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 demonstrated by Professor Sakamoto.
All emphasis in the text except headings is mine.
Does a China that seeks hegemony have any friends.
Leaders who are not elected must constantly demonstrate the legitimacy of their rule through achievements.
The cornerstone of security is the Korean Peninsula.
The year 2018 marks the 150th anniversary of the Meiji Restoration.
As this is a fitting milestone, why not take this opportunity to reflect on the history since the Meiji Restoration and reconsider Japan’s diplomacy and security policy.
Japan now faces the threat of North Korea’s nuclear missile development, and for the past 150 years the Korean Peninsula has been a crucial area for Japan’s security.
From the Meiji era until before the war, self-defense included ensuring the safety of the Korean Peninsula.
The Sino-Japanese and Russo-Japanese wars were fought to prevent large hostile forces from advancing onto the peninsula.
The Korean Peninsula is shaped like a dagger protruding from the Asian continent toward Japan.
Japan had to protect the peninsula for its own defense, even by dispatching troops.
After the war, however, this changed.
Postwar Japan, weary of overseas military deployments, became a country that would not, could not, and did not wish to send troops to the Korean Peninsula even for self-defense.
Yet this does not mean that after the war the Korean Peninsula ceased to be relevant to Japan’s self-defense.
So how should Japan’s self-defense, including the security of the peninsula, be handled.
This came to be managed through cooperation with the United States, namely 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.
In that war, Japan entrusted the security of the peninsula to the actions of the U.N. forces centered on the United States and devoted itself to supporting them by providing bases.
The year after the Korean War armistice, in 1954, when the Self-Defense Forces were established, the Diet passed a resolution prohibiting overseas deployment.
It is clear that the “overseas” referred to here had the Korean Peninsula in mind.
It meant that even if something happened again on the peninsula, the Self-Defense Forces would not be sent.
Sixty years later, in 2014, when the government changed its constitutional interpretation regarding collective self-defense, Prime Minister Shinzo Abe also 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 deploy to the Korean Peninsula.Instead, if necessary, U.S. forces will deploy, and Japan will support them.
This division of roles within the U.S.–Japan alliance allows Japan, unlike before the war, to fulfill its self-defense without directly going to the peninsula.
In recent years this framework has been strengthened considerably through security legislation and new guidelines, but whether Japan can respond effectively to the current North Korea problem remains a severe test.
This article will continue.