Seoul — South Korean President Yoon Suk Yeol seemed to treat a declaration of martial law as if it were a light switch, flipping it on at 11 p.m. Tuesday night, only to be unanimously rebuked in an emergency session of the country’s parliament just two hours later. It took him about three hours from that point to accept defeat and announce that he was lifting the martial law order.

The martial law declaration and revocation within six hours was the fiercest whiplash between military control and democracy that South Korea has endured since it became a democracy in 1987. It appears highly likely to bring a swift end to Yoon’s two-year tenure as the country’s elected leader.

The president’s gamble seemed rooted primarily in his own domestic political isolation and, while short-lived, it was sure to have major ramifications both for Yoon as a politician, and for South Korea as a nation.

Below is a look at what Yoon did, why he did it, and what it could mean for one of Asia’s most vibrant democracies and biggest economies.

What is martial law?

A declaration of martial law is typically used by political or military leaders in a country facing a purported immediate threat to stability or security. It is ostensibly intended to protect the rule of law and citizens by putting military forces in immediate control of a country, suspending the authority of a civilian government and legal system.

Yoon’s order immediately put South Korea’s military in charge of security across the country, froze virtually all existing laws and granted the forces extraordinary powers to detain people without charge and to censor the media.

There was no indication that South Korean troops took advantage of the powers granted to them during the six hours of martial law on Tuesday evening, though there were tense scuffles as forces blocked access to the parliament building and throngs of angry citizens turned up to protest Yoon’s sudden move.

Why did South Korea’s president impose martial law?

“I declared martial law at 11:00 last night with a firm will to save the country against anti-state forces that are trying to paralyze the essential functions of the state and destroy the constitutional order of liberal democracy,” Yoon told his nation in a televised address, claiming the declaration would protect south Korea from a “threat of the North Korean communist forces.”

But he never identified any specific military movements by the North, and his shock move appeared to have been directed more at what he called the “legislative dictatorship” of his own country’s opposition Democratic Party.

Yoon has seen his approval rating fall for several months, and with the opposition in control of the parliament for the last two years, he’s struggled to move forward any of his political objectives. He’s also faced criticism for dismissing multiple calls for independent investigations into financial scandals involving himself and his wife.

He complained Tuesday that the opposition had effectively left him unable to govern, including by proposing nearly two dozen impeachment motions against his conservative government and slashing his national budget by at least $700 billion dollars.

But despite Yoon’s political isolation and falling support among voters, few in the country anticipated a counterattack as dramatic as the declaration of martial law.

What will the martial law declaration mean for South Korea?

“Whichever way this shakes out, this is a major setback for what has been seen as a democratic stronghold in the Asia Pacific for the last 44 years,” said CBS News national security contributor Sam Vinograd, a former senior Homeland Security official.

“The overall perception of South Korea as a stable democracy has been tarnished at a time when an aggressive China and overall retrenchment from democracy globally are big concerns for U.S. national security,” said Vinograd, who’s now the geopolitical lead at the Brunswick Group think tank in Washington.

The White House, in a statement late Tuesday in Washington, expressed relief that Yoon had rescinded his martial law declaration.

“Democracy is at the foundation of the U.S.-ROK alliance, and we will continue to monitor the situation,” an administration spokesperson said, referring to South Korea by the initials of its official name, the Republic of Korea. 

Washington has a deeply vested interest in stability in South Korea. About 28,500 U.S. troops are stationed in the country, largely to deter any aggression by nuclear-armed North Korea, but also as a deterrent against an increasingly assertive China.

South Korea’s capital Seoul lies just 30 miles south of the Demilitarized Zone — the no-man’s land created to separate the North and South when an armistice ended combat in the Korean War in 1953. The two countries technically remain at war as there was never a formal treaty, and tension between the Koreas has escalated in recent years, including under Yoon, who’s taken a harder line on the North than his predecessor.

“The Biden administration is going to be faced with some very difficult decisions about what to say and do,” said Vinograd. “South Korea is one of our closest allies, but this move seems to have come as a surprise to the White House.”

“South Korea is a strong balancing factor against North Korea and against communist China,” Vinograd said, adding that both the North and Moscow “are likely cheering the democratic upheaval in South Korea.”

“They see any signs of instability in South Korea as something that they can take advantage of… Without a vibrant democracy in South Korea, forces within China, within North Korea, will likely feel emboldened, and overall, democratic tendencies in the Asia Pacific will likely take a hit as well.”

Yoon faces calls to resign, threat of impeachment

Yoon looked increasingly likely to lose his job Wednesday after his seemingly dramatic miscalculation of political support.

The Democratic Party called quickly for Yoon to step down or face impeachment, and along with five smaller opposition parties, it submitted a bill in parliament Wednesday to impeach the president, with voting expected on the measure Friday or Saturday.

“It was clearly revealed to the entire nation that President Yoon could no longer run the country normally. He should step down,” senior Democratic Party lawmaker Park Chan-dae said in a statement, urging Yoon not to wait to be forced out.

South Korea’s parliament, the National Assembly, can impeach the president if over two-thirds of lawmakers vote in favor of the move. If it happens and he doesn’t resign first, South Korea’s constitutional court will then hold a trial to either confirm or deny the impeachment motion. Six of the nine justices on the court must back an impeachment for it to go ahead.

Yoon’s PPP holds 108 seats in the 300-member legislature, but even his own party appeared unlikely to back the embattled president too robustly. Its leader called Wednesday for the country’s defense minister to be sacked and the entire cabinet to resign, and the unanimous vote overruling his martial law declaration was a clear indication of the level of opposition to his conduct.

South Korean stocks tumble after martial law declaration

The streets of Seoul appeared largely normal Wednesday despite the overnight tumult. While police were out in force amid renewed protests against Yoon around the parliament, the usual morning rush hour traffic choked roads and railways.

More protests were expected, however, and South Korea’s biggest labor union coaltion, the Korean Confederation of Trade Unions, declared a nationwide strike and said it would hold a rally in the capital until Yoon left office.

The U.S. Embassy in Seoul urged American nationals in the city to avoid areas where protests were taking place, and some of the country’s biggest employers, including the LG Electronics brand, urged employees to work from home.

The unrest also took a toll on Asian stocks, with South Korean shares falling about 1.4% Wednesday and the country’s currency, the won, stable but still close to a two-year low against the dollar.

South Korean Finance Minister Choi Sang-mok and national bank governor Rhee Chang-yong gathered their deputies overnight for emergency meetings, and the finance ministry promised to take whatever measures were necessary to prop up falling share prices, according to the Reuters news agency.

Reuters said canned goods and staples such as instant noodles and bottled water flew off store shelves overnight as South Koreans feared a possible lingering political crisis.

“South Korea is no stranger to martial law,” Vinograd told CBS News, noting that the measure had been declared at least 15 times by various authoritarian regimes since the country’s founding in 1948.

“I’m deeply disturbed by this kind of situation,” Seoul resident Kim Byeong-In, 39, told Reuters overnight, “and I’m very concerned about the future of the country.”

contributed to this report.