At the heart of the proposal, reportedly unveiled by Nakatani to Hegseth during a meeting in Tokyo on March 30, is a vision of East Asia as a single, interconnected “theatre” of operations. This expansive zone would encompass the East China Sea, South China Sea and the Korean peninsula, where Japan, the United States, and regional allies would collaborate more closely to counter rising military threats.
“Japan plans to deepen partnerships by viewing Japan, the US, Australia, the Philippines, South Korea and others as [partners focusing on] a single theatre,” Nakatani was quoted as telling Hegseth, who reportedly responded positively to the proposal.
But the plan has triggered concerns in South Korea that the mission of US Forces Korea (USFK) could shift from defending against North Korea to containing China.

“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,” the Korea JoongAng Daily reported.