Senior U.S. military leaders press Seoul onto the frontline against China

SEOUL, South Korea — A senior U.S. military commander, the second one in three days, promoted South Korea as a forward player in U.S.-led efforts in the region to deter and contain China — a shift in defense strategy that would be seismic for Seoul.

In a country whose military has traditionally focused on North Korea, and where the Lee Jae-myung government has made clear its enthusiasm for improving relations with its key trade partner, China, the American comments have created a buzz.

The timing may be germane. The military commander made the remarks just two weeks after President Trump, on a visit to South Korea, approved Mr. Lee’s request for a proprietary U.S. weapon that Seoul has sought for more than two decades: nuclear-powered attack submarines.

Gen. Xavier Brunson, commander of U.S. Forces Korea, called Monday for a new understanding of South Korea’s geostrategic positioning in the region, especially regarding China.

His written commentary, published on the USFK website, followed comments by Adm. Daryl Caudle, U.S. Navy chief of operations, three days earlier.

Speaking to Korean reporters during a trip to assess South Korean shipbuilding capabilities, Adm. Caudle voiced a “natural expectation” that the nuclear boats South Korea is set to procure courtesy of the U.S. will join efforts to deter China.

Gen. Brunson focused on the location of the Korean Peninsula, the only chunk of the Asian mainland with U.S. boots on its ground, as “a strategic pivot point” on the map.

“Forces already positioned on the Korean Peninsula are revealed not as distant assets requiring reinforcement, but as troops already positioned inside the bubble perimeter that the U.S. would need to penetrate in the event of crisis or contingency,” he wrote.

That perimeter has long been defined as the First Island Chain, a ring of nations — the Philippines, Taiwan and Japan — off the eastern coasts of the Chinese mainland. Combined, they form an offshore barrier that Beijing’s naval forces would have to break through or bypass to reach the open Pacific.

South Korea lies inside the chain.

“Distance analysis reveals Camp Humphreys’ proximity to potential threats: approximately 158 miles from Pyongyang, 612 miles from Beijing and approximately 500 miles from Vladivostok,” the senior U.S. general in Korea wrote. “Korea is positioned to address northern threats from Russia while simultaneously providing western reach against Chinese activities in the waters between Korea and China.”

Camp Humphreys, which became fully operational in 2018, is the largest U.S. military base in Korea and the largest base outside the U.S. for American forces worldwide. It is 40 miles south of Seoul on Korea’s western, Yellow Sea-facing coast.

As such, Camp Humphreys and its two satellite air bases, Osan and Kunsan, appear more postured against China than against the Demilitarized Zone separating South Korea and North Korea.

“From Beijing, American forces at installations like Osan Air Base appear not as distant threats requiring complex power projection, but as immediately proximate capabilities positioned to achieve effects in or around China,” Gen. Brunson wrote.

Moreover, without mentioning Taiwan — the democratic island claimed by Beijing, toward which Washington has customarily applied the principle of “strategic ambiguity” — he made clear the convergent effect of three U.S. allies in the region: Korea, Japan and the Philippines.

“When these three mutual defense treaty partners are viewed as vertices of a triangle rather than isolated bilateral relationships, their collective potential becomes clear,” he said.

Adm. Caudle focused on the role of the nuclear submarines, the numbers and delivery dates of which are unknown, that the South Korean navy is expected to acquire.

“With that type of capability, I think the United States would expect that partnership … working as an alliance together, to meet our combined goals on what the United States considers to be our pacing threat, which is China,” he said.

For Korea’s top brass, that would present a dramatic change in posture. Though South Korea and China fought each other during the Korean War, the two established full diplomatic relations in 1992.

Economic relations have since surged. In 2009, China surpassed the U.S. as the largest buyer of Korean exports, although the U.S. regained its position in 2024, with both nations accounting for a 20% share.

The Lee administration, in particular, has bristled at suggestions that South Korean soil be used to counter China.

In October, South Korean Defense Minister Ahn Gyu-back told the National Assembly’s National Defense Committee that he “cannot agree” with suggestions that USFK’s role included deterring China.

Officers and officials have customarily said their forces cannot commit to a defense of Taiwan or to other regional contingencies on the basis that such crises could offer opportunities for North Korea to attack South Korea.

In a fact sheet published on the White House website detailing follow-up after the Lee-Trump summit in October, just one line was devoted to Taiwan: The two presidents “emphasized the importance of preserving peace and stability across the Taiwan Strait.”

Chun In-bum, a retired South Korean general, told The Washington Times that during his entire career, he never conducted, nor had he ever heard of, any training or contingency planning for a Taiwan scenario.

Adm. Caudle suggested that Seoul’s military needs to think beyond the peninsula.

“With great power comes great responsibility,” he said. “I think there will be a responsibility for Korea to deploy those submarines globally and move away from just being a regional navy to a global navy.”