Interview: Intelligence sharing with US weakened under Yoon, says ex-NIS deputy director

South Korea's intelligence sharing with the US appears to have weakened during former President Yoon Suk Yeol's nearly three years in office, according to Rep. Park Sun-won, who served as the National Intelligence Service's deputy director.

Speaking to The Korea Herald on Monday, Park said that the NIS' apparent failure to learn in advance that the US Department of Energy would place South Korea on a watchlist in January could be one indication of poor intelligence cooperation between the allies.

Park argued that as a result of Yoon's "hawkish" North Korea policies, inter-Korean relations have deteriorated, which has put a dent in Seoul's ability to gather intelligence on Pyongyang.

"Intelligence sharing is a two-way street. Our intelligence agency had less it could share with its US counterparts because there isn't much room to carry out intelligence operations against North Korea. The US started sharing less with us because we don't have much to give back," he said.

Park said comments by some in the then-ruling bloc about South Korea potentially acquiring its own nuclear weapons also likely played a role in the drifting apart of the intelligence and security authorities of the two countries.

"Talking about going nuclear is a big deal. They say it's just rhetoric, but such talk is not acceptable in the diplomatic arena. That must have alarmed Korea watchers in Washington," he said.

Park said while Yoon claimed to have elevated ties with the US, the Energy Department in Washington's decision to designate South Korea a sensitive country "suggested otherwise."

The indictment of Sue Mi Terry, a former Central Intelligence Agency analyst, was also a "public humiliation" for the NIS, Park said. The indictment, unsealed in July last year, alleged that NIS officials gifted Terry with luxury handbags and concealed payments in return for her favors, such as giving them access to members of the US Congress.

But the ultimate blow, Park said, was Yoon's imposition of martial law, which "was brief but made a lasting impact" on where South Korea stands on the map of international relations.

According to Park, the Democratic Party's then-chair Rep. Lee Jae-myung began planning around July last year how his party would respond if Yoon declared martial law.

"As early as last July, I remember Lee asking what our party could do in the event Yoon imposes martial law. We had been noticing signs of such discussions taking place among some military leaders and Cabinet members," Park said.

Park said that about two months before Yoon's botched martial law decree on Dec. 3, 2024, the Democratic Party had also warned Woo Won-shik, the National Assembly speaker, about the possibility.

"The speaker took it very seriously. He even spoke about staying overnight at the National Assembly on a random basis so that he could convene a plenary session immediately to overturn martial law," the lawmaker said. "So we were well-rehearsed for what unfortunately ended up happening."

On the night martial law was declared, inside the plenary chamber, Park orchestrated the response of his fellow Democratic Party lawmakers, telling them to delete sensitive conversations on Telegram and other messaging platforms. The lawmaker, who is well-networked within the intelligence community, also received tips that the troops who broke into the Assembly compound were from the Army's elite counter-terrorism unit.

Park accused the NIS director, Cho Tae-yong, of being negligent for claiming that he had no knowledge of Yoon's martial law plans, which the lawmaker suspects were concocted at least months prior.

"If he truly didn't know, which I highly doubt, then I would say he was incompetent as the chief of our intelligence service. If he did know, then he would be complicit," he said.