South Korea's president accepted the resignation of his defense minister Thursday as Opposition parties moved to impeach both men over the stunning yet short-lived imposition of martial law that brought armed troops into Seoul streets.

The main Opposition Democratic Party and other small Opposition parties submitted a joint motion to impeach President Yoon Suk Yeol on Wednesday over his martial law declaration the previous night. Martial law lasted about six hours, as the National Assembly quickly voted to overrule the president, forcing his Cabinet to lift it before daybreak Wednesday.

On Thursday, Yoon replaced Defense Minister Kim Yong Hyun with Choi Byung Hyuk, a retired four-star general who is South Korea's ambassador to Saudi Arabia, Yoon's office said.

It didn't provide any further comments by Yoon. He hasn't made any public appearances since he announced in a televised address that his government was lifting the martial law declaration.

The opposition parties earlier submitted a separate motion to impeach Kim, alleging he recommended Yoon impose martial law. On Wednesday, Kim offered to resign and apologized for causing disruption and concern to the public. Kim said “all troops who performed duties related to martial law were acting on my instructions, and all responsibility lies with me,” according to the Defense Ministry.

The impeachment motion on Yoon was introduced at a parliamentary plenary session early Thursday, meaning it can be put to a vote between Friday and Sunday. By law, the motion will be scrapped if it isn't voted within 72 hours of its parliamentary introduction. Opposition parties can submit a new impeachment motion if the current one is scrapped or voted down, according to National Assembly officials.

Prospects for Yoon's impeachment isn't clear as Yoon's ruling conservative People Power Party decided Thursday to oppose the motion's passage. Choo Kyung-ho, the floor leader of the PPP, told reporters that his party would hold another meeting to determine how to oppose the motion's passage. Observers say PPP members could simply boycott a floor vote or cast ballots against the motion.

Impeaching him would require support from two-thirds of the single-chamber National Assembly, or 200 of its 300 members. The opposition parties together have 192 seats and they need additional votes from the PPP. Some experts earlier said the motion will likely be passed through parliament as 18 PPP lawmakers, who belong to an anti-Yoon faction in the party, already voted down Yoon's martial law decree together with opposition lawmakers.

But speaking to reporters Thursday, PPP leader Han Dong-hun, head of the anti-Yoon faction, said he would work to ensure that the impeachment motion doesn't pass though he remains critical of Yoon's action, which he described as “unconstitutional.” Han said that there is a need to “prevent damage to citizens and supporters caused by unprepared chaos.”

Experts say rival factions in PPP could unite not to repeat their traumatic experiences following the 2016 impeachment of scandal-ridden conservative President Park Geun-hye, which happened after some lawmakers at her own party voted to impeach her. Park was eventually removed from office and arrested in 2017, and the liberals easily won the presidency in a by-election as conservatives remained in disarray.

If Yoon is impeached, he will be deprived of his constitutional powers until the Constitutional Court rules. Prime Minister Han Duck-soo, who holds the No. 2 position in the South Korean government, would take over presidential responsibilities.

The impeachment motion on Yoon accuses him of attempting a “self-coup” by mobilizing the military. It also says Yoon's declaration failed to meet the constitutional requirements that such steps should only be considered in severe crisis situations. The motion also argues that his move to declare a suspension of political party activities and deploy troops in an attempt to seal the National Assembly amounted to rebellion.

Yoon's martial law declaration, the first of its kind in more than 40 years, harkened back to South Korea's past military-backed governments when authorities occasionally proclaimed martial law and other decrees that allowed them to station soldiers, tanks and armored vehicles on streets or at public places such as schools to prevent anti-government demonstrations. Until Tuesday night and Wednesday morning, such scenes of military intervention had not been seen since South Korea achieved a democracy in the late 1980s.

After Yoon's declaration, troops carrying full battle gear, including assault rifles, tried to keep protesters away from the National Assembly as military helicopters flew overhead and landed nearby.

It wasn't clear how the 190 lawmakers were able to enter a parliamentary hall to vote down Yoon's martial law decree. Opposition leader Lee Jae-myung and National Assembly Speaker Woo Won Shik were seen climbing over walls. As troops and police officers blocked some from entering, they didn't aggressively restrain or use force against others.