The Biggest Winner Of the Japan-South Korea Dispute? China

South Korea’s decision to end an intelligence-sharing agreement with Japan, part of a widening rift between the two U.S. allies, has the Pentagon on edge — and not just because it arrives amid stalled efforts to persuade North Korea to denuclearize. 

“China is the biggest winner here,” said Rob Spalding, a former senior official on President Trump’s National Security Council. “The biggest challenge is the fact that the Chinese, who really want to break up the alliance structure—this just hands them a potent weapon to chip away at it.”

An apparently rattled Defense Department reacted with two statements on Thursday: one in the morning “encouraging” the two sides to work together, then an updated, much stronger missive in the afternoon professing “strong concern and disappointment that the Moon Administration has withheld its renewal” of the framework. 

“We strongly believe that the integrity of our mutual defense and security ties must persist despite frictions in other areas of the ROK-Japan relationship,” Pentagon spokesman Lt. Col. Dave Eastburn said in the later statement. 

Although concerns over North Korea’s growing nuclear arsenal have dominated headlines about Trump’s security strategy in the Indo-Pacific, it’s a resurgent China that Pentagon officials say is the bigger long-term threat. “China is the number one priority for this department,” Defense Secretary Mark Esper told Fox News on Wednesday, in his first televised interview since taking the job. “They are clearly professionalizing and expanding the capacity and capabilities of the military in order to push the United States out of theater.” 

China has long sought to fracture the trilateral alliance between South Korea, Japan, and the United States. The two Asian nations host a combined 80,000 U.S. troops—the linchpin of the U.S. presence in the Indo-Pacific—while the United States has been working with Seoul to urge North Korea to denuclearize. Ryan Hass, the China director on President Obama’s National Security Council, called South Korea’s decision “a major setback for U.S. strategy in northeast Asia,” emphasizing that “alliance cohesion is a critical enabler” of that strategy.

But the relationship between Japan and South Korea is deeply fraught. The 1910 Japanese annexation of the Korean peninsula is still a radioactive political issue in both the north and the south, and the so-called “history wars” over Japanese atrocities—including the taking of an unknown number of Korean women as sex slaves for its soldiers—has raged for decades. Seoul’s decision to end the intelligence agreement comes amid a trade dispute that has plunged relations between the two countries to perhaps their lowest level since they reestablished diplomatic ties in 1965. 

“Under this situation, the government has determined that maintaining the agreement, which was signed for the purpose of exchanging sensitive military intelligence on security, does not serve our national interests,” Kim You-geun, the deputy director of South Korea’s presidential national security office, said in a surprise statement. 

The practical impact of the demise of the intelligence-sharing agreement is difficult to judge. It’s not clear how useful the pact was to either nation. The two nations signed it in 2016 under pressure from Washington; Seoul’s withdrawal means the United States will return to being the hub for information shared separately from Japan and South Korea. That information is related to a host of transregional threats, including North Korea’s nuclear weapons, Chinese intellectual property theft, and military activity in the South China Sea. 

“By definition, you’re destroying combat capability,” said Spalding, one of the key architects of the Trump administration’s National Security Strategy, which prioritizes preparing for potential conflict with nation-state competitors like China and Russia over countering terrorist groups. “Just doing warfare when you have all the same equipment and everybody agrees to treat each other as an equal [is] hard. So imagine if one ally is not talking to the other. There’s no way you can be an effective fighting force.” 

“It’s how Americans get killed, because we’re playing games,” he continued. “You really can’t mess around with how the coalition functions in a war.”

Other analysts have expressed concerns that the broader rift between Japan and South Korea could push Seoul towards exactly the two countries that the United States now considers its top competitors.

“South Korea’s vow to diversify economic supply sources away from Japan could lead South Korea to turn to China or Russia,” write Riley Walters and Bruce Klingner, policy analysts at the conservative Heritage Foundation. 

The United States in the past has acted as a mediator between Seoul and Tokyo. The Obama administration helped bring about a 2015 agreement under which Tokyo apologized for the kidnapping of “comfort women”—women used as sexual slaves—and paid $8 million to Koreans thus seized; in exchange, Seoul declared the issue “finally and irreversibly” over. That agreement has since fallen apart, sparking the current crisis. 

President Trump has expressed ambivalence to intervening, however. In July, said he told Moon, “How many things do I have to get involved in? It’s like a full-time job getting involved between Japan and South Korea.”

“Xi can’t stop laughing at all this,” tweeted MIT security studies professor Vipin Narang.