A South Korean student attends a rally Saturday in Seoul to denounce Japan's new trade restrictions. (Chung Sung-Jun/Getty Images)

In a new salvo in the diplomatic spat between South Korea and Japan, Seoul hit back by pulling out of a military intelligence-sharing agreement with Tokyo. The General Security of Military Information Agreement (GSOMIA), signed in 2016 and up for renewal this fall, allowed for more “seamless intelligence sharing” between the two countries.

This could create wider security issues in Asia. Specifically, the GSOMIA lets Tokyo and Seoul directly exchange sensitive military information — especially regarding North Korean nuclear and missile activity — without needing to go through Washington. The intelligence-sharing pact is now set to expire in November.

Bilateral relations spiraled downward after South Korea’s Supreme Court upheld a lower court’s ruling ordering Japanese firms to compensate unpaid South Korean laborers from Japan’s colonial era (1910-1945). Japan retaliated in early July by restricting exports of materials crucial to South Korea’s semiconductor and electronics industry, then removed South Korea from its “white list” of countries granted preferential trade access to strategic goods.

South Korea responded in kind, announcing its intent to remove Japan from its own white list of preferred trading partners. But the deep-seated trade tiff has now shifted to defense and security issues, with South Korean President Moon Jae-in government’s decision to not renew the GSOMIA.

What about the diplomatic and security costs?

Although the move takes direct aim at Japan, withdrawal from the GSOMIA ultimately decreases South Korea’s own national security and leaves the United States, Japan and Korea less prepared to respond to North Korean provocations.

And Seoul’s decision leaves it isolated diplomatically — Washington and Tokyo both criticized the Moon government’s decision. The Pentagon expressed “strong concern and disappointment” that South Korea had not renewed the GSOMIA, while Secretary of State Mike Pompeo added his concerns about Northeast Asia’s security challenges.

In recent weeks, North Korea has conducted seven short-range missile tests. The latest test, conducted one day after Seoul’s withdrawal from the GSOMIA, makes it difficult to believe the official statement that the GSOMIA is not in South Korea’s national interest.

South Korea’s Blue House has played down the security implications of the move. Deputy national security adviser Kim Hyun-chong stated that South Korea would continue to share limited intelligence with Japan through the Trilateral Information Sharing Arrangement (TISA) among the United States, Japan and South Korea. Under TISA, however, parties negotiate intelligence sharing on a “case by case” basis, and delays could prove costly in a crisis situation.

Pushing back against Japan may cement Moon’s domestic base

Moon’s decision may appear irrational, given the diplomatic and security costs associated with Seoul’s unilateral termination of the GSOMIA. But the ruling Democratic Party may have calculated political advantages in drumming up anti-Japan nationalist sentiment. A July 22 opinion poll from Realmeter placed Moon’s approval rating at 51.8 percent, the highest in eight months. The progressive Hankyoreh newspaper attributed the uptick to the Blue House “standing up” to Japan.

An Aug. 3 poll conducted by SA Consulting found 50.9 percent of respondents backing Moon’s hard-line response to Japan — compared with 45.5 percent of Koreans indicating disapproval. This was true even though the same poll found more respondents believed that South Korea, not Japan, would ultimately face greater damage from the bilateral trade war. The past month has seen a wave of anti-Japan rallies and boycotts in Seoul, hitting Japanese restaurants and retailers such as Uniqlo hard.

The Moon government has framed its anti-Japan stance and withdrawal from the GSOMIA in terms of the national interest. Democratic Party floor leader Lee Young-in supported the Blue House’s statement, arguing that the decision reflected the national interest and “the will of the people.” Likewise, a Hankyoreh editorial, citing Japan’s refusal to negotiate with or respond to South Korean overtures for mediation, put the onus squarely on Japan with the headline: “As the instigator of the conflict, Japan needs to be proactive about finding solutions.”

The GSMOIA wasn’t Moon’s deal

With the GSMOIA’s renewal deadline approaching, and amid growing anti-Japan sentiment, the Moon government may have found an opportune time to scrap a deal that the Democratic Party never supported in the first place.

The party strongly opposed the GSOMIA in 2016 and helped derail negotiations in 2012. The deal was signed amid the Park Geun-hye scandal in November 2016, and the then-opposition Democratic Party criticized the Park government for hastily signing it as a way to deflect public attention from Park’s growing political crisis.

In contrast to conservative parties, the Democratic Party and other progressive parties in South Korea have generally discounted threats from North Korea and remained more suspicious of Japan. Given their progressive views on national security and foreign policy, some Blue House officials may not have seen the GSOMIA in the same light as Washington or Tokyo does.

Or is this a political diversion?

In a twist of irony, the Moon government may be employing diversionary tactics of its own as it faces a mounting scandal, with Cho Kuk, tapped to be the next justice minister and a former senior secretary to Moon, at the center. There are allegations that Cho’s daughter received scholarships covering multiple semesters to attend medical school, despite her subpar academic performance and lack of financial need. Revelations of preferential academic treatment, a cardinal sin among South Koreans, have sparked student protests across several campuses.

The opposition Liberty Korea Party has also called for an investigation into allegations of corruption involving Cho’s family and personal networks. Although the brewing scandal isn’t likely to top “Choi Soon-sil-gate” — which brought down Park in late 2016 — whether intentional or not, the GSOMIA has given the Moon government its “wag the dog” moment.

The bottom line? Seoul, Tokyo and Washington face shared security challenges that would seem to require close coordination on intelligence. Russia’s violation of South Korean airspace in July and the proliferation of North Korean short-range missile tests add to the threat of North Korea’s nuclear program.

But recent steps by Seoul and Tokyo, and the inability of the Trump administration to patch strained relations, have left experts wondering about the way forward for Korea-Japan relations.

Andrew Yeo is an associate professor of politics at the Catholic University of America in Washington and the author of “Asia’s Regional Architecture: Alliances and Institutions in the Pacific Century (Stanford University Press, 2019).