TOKYO — Troops surround South Korea's parliament overnight after the president declared martial law. He accused pro-North Korean forces of plotting to overthrow one of the world’s most vibrant democracies. Lawmakers voiced outrage, and hastily voted to end the declaration in an early-morning session.

Confusion, rumor and fear were spreading through South Korea before dawn Wednesday after the sudden edict by President Yoon Suk Yeol, the first martial law since more than four decades ago when the country was controlled by a dictatorship.

The declaration and a rushed vote by lawmakers to overturn it were moments of high drama for an unpopular leader who has struggled with political deadlock in an opposition-dominated parliament and scandals involving him and his wife.

While there was no direct evidence presented, Yoon raised the specter of North Korea as a destabilizing force. Yoon has long maintained that a hard line against the North is the only way to stop Pyongyang from following through on its nuclear threats against Seoul.

Amid the surreal scenes of troops massing around parliament, here are some things to know as this story unfolds:

Immediately after Yoon's declaration the military chief called in key commanders for talks. South Korean troops set up barricades and then made their way into parliament. The leader of the main opposition, which controls parliament, ordered lawmakers to return to the building, where they eventually voted to lift the declaration of martial law.

But there were far more questions than answers as the uncertainty stretched into the early morning hours.

Yoon's declaration of an emergency martial law was accompanied by an accusation that the opposition was engaged in “anti-state activities plotting rebellion.” But he did not explain what that means, and provided no specific evidence.

The vague statement is reminiscent of the heavy-handed tactics of the South Korean dictatorships that ended in the late 1980s. A series of strongmen repeatedly invoked North Korea when struggling to control domestic dissidents and political opponents.

The opposition lambasted Yoon's move as undemocratic. Opposition leader Lee Jae-myung, who narrowly lost to Yoon in the 2022 presidential election, called Yoon’s announcement “illegal and unconstitutional.”

But the sudden declaration was also opposed by the leader of Yoon's own conservative party, Han Dong-hoon, who called the decision “wrong” and vowed to “stop it with the people.”

“The people will block the president’s anti-constitutional step. The military must be on the side of the public in any case. Let’s resolutely oppose it,” Kim Dong Yeon, the opposition party governor of Gyeonggi province, which surrounds Seoul, wrote on X.

Average South Koreans were in shock. Social media was flooded with messages expressing surprise and worry over Yoon’s announcement.

“Martial law? I thought it was deepfake content, but is it really a martial law decree?,” one X user wrote.

“I first thought about a war with North Korea when he said he would impose a martial law,” another X user wrote.

There were quick claims that the emergency declaration was linked to Yoon’s political struggles.

His approval rating has dropped, and he has had little success in getting his policies adopted by a parliament that has been controlled by the opposition since he took over in 2022.

Conservatives have said the opposition moves are political revenge for investigations into the opposition leader, who is seen as the favorite for the next presidential election in 2027.

Just this month, Yoon denied wrongdoing in an influence-peddling scandal involving him and his wife. The claims have battered his approval ratings and fueled attacks by his rivals.

The scandal centers on claims that Yoon and first lady Kim Keon Hee exerted inappropriate influence on the conservative ruling People Power Party to pick a certain candidate to run for a parliamentary by-election in 2022 at the request of Myung Tae-kyun, an election broker and founder of a polling agency who conducted free opinion surveys for Yoon before he became president.

Yoon has said he did nothing inappropriate.

South Korea became a democracy only in the late 1980s, and military intervention in civilian affairs is still a touchy subject.

During the dictatorships that emerged as the country rebuilt from the destruction of the 1950-53 Korean War, leaders occasionally proclaimed martial law that allowed them to station combat soldiers, tanks and armored vehicles on streets or in public places to prevent anti-government demonstrations.

Such scenes are unimaginable for many today.

The dictator Park Chung-hee, who ruled South Korea for nearly 20 years before he was assassinated by his spy chief in 1979, led several thousand troops into Seoul in the early hours of May 16, 1961, in the country’s first successful coup. During his rule, he occasionally proclaimed martial law to crack down on protests and jail critics.

Less than two months after Park Chung-hee’s death, Maj. Gen. Chun Doo-hwan led tanks and troops into Seoul in December 1979 in the country’s second successful coup. The next year, he orchestrated a brutal military crackdown on a pro-democracy uprising in the southern city of Gwangju, killing at least 200 people.

In the summer of 1987, massive street protests forced Chun’s government to accept direct presidential elections. His army buddy Roh Tae-woo, who had joined Chun’s 1979 coup, won the election held later in 1987 thanks largely to divided votes among liberal opposition candidates.