Opposition party lawmakers and citizens chant slogans in front of the main building of the National Assembly in Seoul, Wednesday, urging President Yoon Suk Yeol to step down over what they described as an illegal and unconstitutional declaration of martial law. Yonhap

President Yoon Suk Yeol's brief declaration of martial law has plunged him into the most severe leadership crisis of his tenure, as the opposition bloc pushes for his impeachment, accusing him of treason.

Six opposition parties, including the main opposition Democratic Party of Korea (DPK), jointly submitted a bill to the National Assembly, Wednesday, to oust Yoon. They plan to vote on the bill as early as Friday morning.

The latest developments follow the president's abrupt declaration of martial law at 10:23 p.m. on Tuesday, citing the urgent need to eradicate "anti-state forces," targeting the opposition, which has repeatedly blocked his personnel appointments and budget proposals.

While around 280 soldiers entered the Assembly compound and even the main building, 190 lawmakers managed to reach the main hall and voted at around 1 a.m. on Wednesday, demanding that the president lift the martial law. As the law requires the president to comply with the Assembly's vote, Yoon announced his decision to comply at around 4:20 a.m., bringing an end to the six-hour crisis.

The opposition bloc argued that the martial law did not meet any of the required conditions for declaration — such as maintaining public order during times of war or other national emergencies. They contended that declaring martial law under none of these circumstances could constitute a violation of the constitutional order, which could serve as grounds for impeachment.

Opposition party lawmakers submit to the National Assembly's legislative office in Seoul, Wednesday, a motion to impeach President Yoon Suk Yeol. Yonhap

The motion was co-authored by six opposition parties — the DPK, Rebuilding Korea Party (RKP), New Reform Party, Progressive Party, Basic Income Party and Social Democratic Party.

All 191 lawmakers from the six opposition parties participated in submitting the motion.

A DPK official told reporters that the motion is expected to be formally introduced during a plenary session in the early hours of Thursday. Once the impeachment motion is submitted, a vote must take place within 24 to 72 hours, meaning the vote could start as early as Friday morning.

Nationwide condemnation

Since Yoon's unexpected declaration of martial law, the push for impeachment has been widely anticipated. The president's unilateral and legally questionable announcement sparked nationwide condemnation, not only from the opposition but also from the public. The resulting shock and controversy have seemingly paved the way for the impeachment effort.

"We'll seek Yoon to be punished for treason for the unconstitutional, illegal martial law," DPK spokesman Rep. Jo Seoung-lae said. "We'll file a complaint against Yoon, Defense Minister Kim Yong-hyun and Interior Minister Lee Sang-min, and seek to impeach them."

The defense minister is believed to be the one who suggested the martial law to Yoon, while the interior minister is responsible for overseeing the police forces.

Democratic Party of Korea's floor leader Park Chan-dae delivers a speech during an emergency rally at the National Assembly in Seoul, Wednesday. Yonhap

DPK floor leader Park Chan-dae said during a protest at the Assembly, "It has been confirmed that Yoon is in such an abnormal state of mind that he should not be allowed to perform the duties of his office for even a single minute or second. His judgment and awareness of the situation are far from normal."

He added, "The declaration of martial law violates both the procedural and substantive aspects of the Constitution and the law, providing full grounds for impeachment. Yoon is the leader of a rebellion, as defined by our Constitution. As the leader of a rebellion, Yoon must immediately step down from the presidency."

DPK leader Rep. Lee Jae-myung also raised his voice, saying that the public can no longer endure or forgive this.

"The president is a servant of the people. Can you believe the reality in which the president mobilizes troops, armed with taxes paid by the people, to point guns at the very people they serve?" he said.

The DPK leader also warned that "there is a chance that Yoon may address shortcomings and try again. I believe they may wage localized battles, but we must remain vigilant and fight together. Let us fight alongside our great people to create a world where the people truly live as the masters of this country."

Civic organization members urge President Yoon Sul Yeol to step down for his martial law declaration, during a rally in central Seoul, Wednesday. Korea Times photo by Choi Won-suk

Impeachment vote

The impeachment motion requires the attendance of more than half of the Assembly members and the approval of at least two-thirds of those present to pass. This means that more than 200 votes out of 300 are needed if all Assembly members attend the vote. Additionally, at least eight lawmakers from the ruling People Power Party (PPP) must join the opposition in supporting the motion.

If the impeachment motion is passed, Yoon's authority will be immediately suspended, and Prime Minister Han Duck-soo will assume the role of acting president. Yoon's exercise of power will be suspended until the Constitutional Court reaches a decision on the impeachment.

It remains unclear how many PPP members will support the motion.

While PPP chief Han Dong-hoon has taken a critical stance against the martial law declaration, the pro-Yoon faction within the party has adopted a more cautious approach.

During Wednesday morning's parliamentary vote to repeal the martial law, 18 pro-Han lawmakers participated and voted in favor, while pro-Yoon lawmakers did not attend the session.

Prime Minister Han Duck-soo, center, arrives at the Government Complex Seoul, Wednesday. Yonhap

Meanwhile, all senior presidential aides, including Chief of Staff Chung Jin-suk, Policy Chief Sung Tae-yoon, National Security Advisor Shin Won-shik, and senior secretaries, submitted their resignations to Yoon on Wednesday morning. It is said most of them were unaware of the martial law declaration plan until it was announced.

However, the likelihood of these resignations being accepted is slim.The fallout from the martial law declaration has completely undermined Yoon's political momentum, making it unlikely that the presidential office will make any further personnel changes at this time.

The prime minister also issued a statement, stating that he takes full responsibility for the events that have led to this situation.

"Until the very end, I will work with the Cabinet members to serve the people. From this moment forward, I ask all public officials in every department to fulfill their duties to ensure that the nation's stability and the daily lives of the people continue without disruption," Han said.