South Korea’s impeached president, Yoon Suk-yeol, faces arrest along with top military officers in what is sure to deepen the chasm between Korean conservatives and leftists in an already highly divided society.

Three government agencies are eager to detain Mr. Yoon on charges ranging from abuse of power to insurrection for his abortive martial law decree after he failed to appear Sunday at the prosecutor’s office for questioning.

The three agencies, including the national police and the corruption investigation office as well as the prosecutor’s office, are “engaged in a turf war for investigating Yoon’s coup attempt,” according to an anti-Yoon website named Blue Roof. “All of them have said they will seek to arrest Yoon,” said the website, run by Korean-Americans highly critical of his administration.

Mr. Yoon’s arrest would inevitably heighten pressure on the Constitutional Court to approve the impeachment motion narrowly adopted Saturday by the National Assembly. His case revives bitter memories of the arrest of the former president, Park Geun-hye, also a conservative, who was impeached, ousted and jailed in 2017 after weeks of mass protests.

The overwhelming impression is that Mr. Yoon, if not guilty of an “insurrection” or “coup against the government” as claimed, has shown terrible judgement that may compromise defense against North Korea and also intensify differences on domestic issues, notably the economy.

“President Yoon has done irreparable damage to South Korea’s ability to carry out his foreign and security policies,” said a long-time Korea expert at the Heritage Foundation, Bruce Klingner, years ago with the CIA.

Perhaps the greatest concern, as Mr. Klingner made clear in an email to the Sun, is that Mr. Yoon’s ouster, regardless of whether or not he’s in prison, would undo gains achieved during his presidency in the military alliance with Washington, reconciliation with Japan, and Seoul’s role in defense of the entire Indo-Pacific.

The Minju, or Democratic Party, engineered his impeachment by five votes above the 200 needed in the 300-seat assembly, including a dozen votes from Mr. Yoon’s own People Power Party. The Minju leader, Lee Jae-myung, is already looking ahead to the election that would be held 60 days after approval of the impeachment decree by the constitutional court.  

Six of the court’s nine members must approve the decree, but the court now has only six sitting judges. A Korean analyst, talking to the Sun, rated Mr. Yoon’s chances of surviving impeachment at “50-50” regardless of whether he’s in jail.

Having narrowly lost to Mr. Yoon in the 2022 presidential election, Mr. Lee would be almost sure to run  in a snap election even though he faces multiple corruption charges in real estate and bribery scandals that have nothing to do with the current crisis.

The fear is that Mr. Lee, if elected, would reverse many of the gains made during Mr. Yoon’s presidency in Korean-American relations. Said Mr. Klingner: “A newly-elected progressive president would resume the party’s conciliatory approach to North Korea, reducing pressure and offering massive economic benefits with few conditions in hopes of moderating Pyongyang’s behavior.”

Any Minju successor, Mr. Klingner warned, “would likely cancel trilateral military exercises, revoke the Camp David agreement on linking the three countries’ missile alert systems, and resist U.S. efforts for a greater South Korean regional security role against the encroaching Chinese threat.”

A retired American army colonel, David Maxwell, veteran of five tours in South Korea in the special forces, agrees — to a point.

The political opposition in Korea believes “weakening” the Korean-American alliance and “undermining trilateral cooperation with Japan and the U.S. would somehow create the conditions” for North Korea and its two huge allies, China and Russia, “to reduce their hostile policies,” he tells the Sun.

Vice president of the Center for Asia-Pacific Strategy, Colonel Maxwell remains irrepressibly optimistic.

“The military’s priority is on protecting South Korea, its democracy, and its people,” he said. The alliance “has weathered many storms over the past seven decades,” he went on, but South Korea and America have “the world’s best bilateral combined command “ and can “defend the security interests of both the ROK and US.”