Japan’s ‘one theater’ plan with U.S. raises concern in Korea over shifting military focus

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Japan’s ‘one theater’ plan with U.S. raises concern in Korea over shifting military focus

Published: 17 Apr. 2025, 12:09

Audio report: written by reporters, read by AI

U.S. Secretary of Defense Pete Hegseth, left, shakes hands with Japanese Prime Minister Shigeru Ishiba at the prime minister's office in Tokyo on March 30. [AP/YONHAP]

Japan's Minister of Defense reportedly proposed a "one theater" concept to the United States that would combine the Korean Peninsula, East China Sea and South China Sea into a single operational and war zone — raising concerns in South Korea that this may shift the U.S. military’s focus on the peninsula from North Korea to China.

If the United States implements the “one theater” concept to effectively contain China, the mission and nature of U.S. Forces Korea (USFK) will inevitably change from defending against North Korea to containing China, according to sources.

Will the USFK’s operational area expand?

The Asahi Shimbun reported on Tuesday that Japanese Defense Minister Gen Nakatani told U.S. Secretary of Defense Pete Hegseth during a visit to Japan last month, "let’s create a single theater that includes Japan, the U.S., Australia, the Philippines and South Korea."

Hegseth responded positively, and the proposal was also discussed in his meeting with Japanese Prime Minister Shigeru Ishiba, according to the newspaper.

A theater in military terms refers to a geographic area where ground, naval and air battles can occur. Though the specific geographical scope of Nakatani’s "one theater" idea is unclear, it appears to suggest a unified area that integrates the Korean Peninsula, East China Sea and South China Sea.

This could be read as potentially opening the door to the USFK being deployed in conflicts outside the Korean Peninsula, including a possible contingency in the Taiwan Strait or the South China Sea.

China would likely be the main adversary in this integrated “one theater.” Japan's intent seems to be binding U.S. forces in East Asia more tightly while sharing the burden of countering China with South Korea, Australia and the Philippines. While even some in Japan call the proposal premature, experts say it broadly aligns with U.S. strategic goals to contain China more efficiently in the region.

U.S. Secretary of Defense Pete Hegseth attends a joint news conference with Gen Nakatani, Japan's Defense Minister, in Tokyo on March 30. [REUTERS/YONHAP]

“In any theater reorganization, unified command is key, so questions about the chain of command between the U.S. Forces in Japan and South Korea would inevitably arise,” said a South Korean military source on the condition of anonymity. "As the U.S. is already reviewing how to optimize its forward-deployed forces in Asia, South Korea needs to ensure that any changes don’t undermine the role and status of the USFK.”

U.S. Forces Japan Commander taking over?

Should the concept become reality, some fear Japan could gain the lead in U.S. force restructuring in East Asia.

Experts in South Korea note that it was former Japanese Prime Minister Shinzo Abe who originally proposed the U.S.-adopted Indo-Pacific strategy under the U.S. President Donald Trump’s first administration, meaning Washington may not easily dismiss this new Japanese proposal.

The United States is already considering upgrading the U.S. Forces Japan commander from a three-star to a four-star general — effectively turning Japan into a rear base against China, according to sources.

If the Trump administration’s broader push for overseas command integration and troop reductions continues, it may seek to balance the addition of a four-star command in Japan by downsizing another, such as the USFK.

Gen Nakatani, Japan's Defense Minister, speaks during a joint news conference with U.S. Secretary of Defense Pete Hegseth, at the Ministry of Defense in Tokyo on March 30. [REUTERS/YONHAP]

The worst-case scenario is that such efficiency-driven integration undermines South Korea’s operational control transfer plans, shaking up the status of the Combined Forces Command.

"From the U.S. perspective, unifying the theater for China deterrence is efficient,” said Lee Sang-kyu of the Korea Institute for Defense Analyses (KIDA). “But if that coincides with the next South Korean administration’s plans to regain wartime operational control, the status of the USFK could be diminished."

Under the current transition framework, South Korea would take command of the Combined Forces Command, with the U.S. military taking the deputy commander role.

Observers speculate that if the transfer occurs, the U.S. four-star general currently leading the USFK may be downgraded and simultaneously serve as the deputy commander of the combined command. That would further tip the balance of command in favor of U.S. Forces Japan.

U.S. Secretary of Defense Pete Hegseth and Japan's Defense Dinister Gen Nakatani meet at the Ministry of Defense in Tokyo on March 30. [REUTERS/YONHAP]

Concerns intertwined with operational control

However, military experts argue that the U.S. Forces Korea and U.S. Forces Japan differ in mission and structure, making immediate command integration unlikely.

The South Korea-U.S. Combined Forces Command is vertically integrated, while the U.S. military’s relationship with Japan’s Self-Defense Forces is more horizontal and loose.

Moreover, the USFK units are assigned specific operational tasks in detailed plans with South Korea, meaning any mission shift would take years to implement.

U.S. Secretary of Defense Pete Hegseth gives his opening speech at the beginning of his meeting with Japanese Prime Minister Shigeru Ishiba at the prime minister's office in Tokyo on March 30. [AP/YONHAP]

That’s why many believe it’s unlikely the "one theater" concept will see results within Trump’s second term. Even within Japan’s Ministry of Defense, there is caution, with Asahi Shimbun quoting voices saying, "we shouldn’t be using such a strong term like 'theater' publicly before defining its contents."

"If South Korea doesn’t actively support U.S. strategy, Washington may lean further toward Japan,” said Park Won-gon, a professor of North Korean studies at Ewha Womans University. “Ultimately, how much influence U.S. Forces Japan gains over the Korean Peninsula depends on Seoul. Even if the ‘one theater’ becomes reality, we should guide it in a way that strengthens deterrence against North Korea by drawing more Indo-Pacific forces into potential Peninsula contingencies."

Translated from the JoongAng Ilbo using generative AI and edited by Korea JoongAng Daily staff.

BY LEE KEUN-PYUNG,LEE YU-JUNG [[email protected]]