From the U.S. perspective it makes sense to have the flexibility to redeploy troops from Korea to assist with a Taiwan contingency. However, this Op-Ed in the Korea Times is against because of some hypothetical possibility of Japanese troops on Korea soil:
Japan’s recent articulation of a “One Theater” doctrine — encompassing the East China Sea, Taiwan Strait and the Korean Peninsula — marks a troubling shift in strategic thinking that risks destabilizing Northeast Asia. Proposed by Japanese Defense Minister Gen Nakatani and seemingly welcomed by U.S. Defense Secretary Pete Hegseth, this doctrine is being presented as a pragmatic response to a volatile regional security environment. In reality, it threatens to undermine national sovereignty, disrupt the delicate geopolitical balance of the Indo-Pacific and draw democratic allies into conflicts not of their choosing.
At its core, the “one battlefield” concept posits that regional flashpoints — such as Taiwan, the Korean Peninsula and the East China Sea — are so interconnected that they must be treated as a unified operational theater. While this might serve military planning purposes, it dangerously flattens political nuance in favor of operational efficiency. It treats sovereign nations not as independent actors with unique security needs, but as interchangeable assets within a broader strategic front defined by Japan and, potentially, the United States.
Of particular concern is the implication that, under this doctrine, U.S. Forces Korea (USFK) could be redeployed from the Korean Peninsula to support operations in the event of a Taiwan contingency. Such a move would not only risk undermining deterrence on the peninsula — where a fragile armistice holds between South and North Korea — but also compromise South Korea’s core defense posture. The Korean Peninsula is not a backwater theater; it is a primary front involving a nuclear-armed adversary. To subordinate Korean security to cross-strait dynamics is both strategically unsound and politically inflammatory.
Historical memory further complicates this issue. Any framework that implicitly or explicitly involves Japanese military activity on or near the Korean Peninsula is politically incendiary. The legacy of Japan’s 1910-45 colonial occupation of Korea continues to cast a long shadow over bilateral relations. For many South Koreans across the political spectrum, the idea of Japanese boots on or near Korean soil — however hypothetical — remains an emotional and constitutional red line. Even under the banner of collective defense, such a scenario would provoke fierce domestic backlash and could fracture regional unity.
You can read more at the link, but it almost sounds like this author rather have North Korean and Chinese Soldiers on ROK territory instead of Japanese. With that said I cannot think of a scenario where Japanese troops would be needed on Korean soil. Japan’s geography makes it an important location to deploy U.S. aircraft, ships, and supplies from for either a Taiwan or North Korea contingency. They Japanese military will not be needed to deploy troops to Korea.
This author is really using the deployment of Japanese troops to Korea as a red herring to obscure the author’s real concern which is the flexibility of the U.S. to deploy troops from Korea for a Taiwan contingency.
