Seoul: 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.
According to Yonhap News Agency, 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.
South Korea, a mature democracy and a central pillar in the U.S.-led security architecture in Asia, must not be treated as a secondary node on another nation's strategic map. The Korean government bears a sovereign responsibility to assert its autonomy and uphold the principle that any foreign military deployment on or near its territory must be subject to Korean consent and command. National defense is not a function of trilateral coordination -- it is a sovereign prerogative.
The United States, for its part, must exercise prudence. Hegseth's commendable work in strengthening trilateral cooperation must not come at the expense of alliance cohesion or democratic legitimacy. Efficiency in military planning must never override political consent. Washington should avoid endorsing doctrines that erase the distinct interests and identities of its allies. True alignment among democracies stems not from uniformity, but from mutual respect. The U.S. should also remember the concept will further intensify its rivalry with China and heighten tension throughout Northeast Asia, as well as the Korean Peninsula.
For its part, South Korea should maintain a calibrated strategic stance. It must preserve its right to ambiguity -- particularly in the context of a potential Taiwan conflict -- while reaffirming its commitment to peace, democracy, and regional stability. Cooperation with Washington and Tokyo should be conditional: coordination, yes; subordination, no.
Japan's "One Theater" doctrine reflects an evolving security posture in an increasingly contested Indo-Pacific. But security cannot be built atop frameworks that erase sovereignty and sidestep history. The peace and autonomy of the Korean Peninsula are not abstract ideals -- they are hard-earned and nonnegotiable. Any doctrine that fails to respect this reality is not just strategically flawed, but dangerously misguided.