During an unscheduled TV address late Tuesday night, South Korean President Yoon Suk Yeol announced the start of martial law, taking effect at 11p.m.

In his speech, the nation’s leader vowed to eliminate what he referred to as “pro-North Korean and anti-state forces,” in reference to the majority-holding opposition in parliament.

The decision sent shock waves through South Korea, which has not been under such a decree since 1979.

Large numbers of protesters descended upon Seoul's National Assembly building, clashing with police officers and demanding that Yoon step down.

At 4:30 a.m., the lawmakers who assembled inside, with some having to bypass barricades to enter the building, voted to overrule the president and lift the decree.

Here are glimpses of a night that tested the strength of democracy in South Korea.

South Korean President Yoon Suk Yeol delivering a speech to declare martial law late Tuesday night. It was South Korea's first martial law declaration in over 40 years, following the end of its military dictatorship in the late 1980s.
South Korean President Yoon Suk Yeol delivering a speech to declare martial law late Tuesday night. It was South Korea's first martial law declaration in over 40 years, following the end of its military dictatorship in the late 1980s. | South Korean Presidential Office / AFP-JIJI

Protesters rally outside the main gate of the National Assembly building. South Korea's constitution allows the president to declare martial law during “wartime, war-like situations or other comparable national emergency states” or situations requiring military intervention to ensure peace and order.
Protesters rally outside the main gate of the National Assembly building. South Korea's constitution allows the president to declare martial law during “wartime, war-like situations or other comparable national emergency states” or situations requiring military intervention to ensure peace and order. | Chang W. Lee / The New York Times

People chant
People chant "end martial law" outside the National Assembly early Wednesday morning following the president's announcement. | AFP-JIJI

Protesters gather following the president's martial law declaration. Local media reported that a presidential declaration of martial law could significantly curtail freedom of speech, as the Constitution permits restrictions on press freedom under such circumstances.
Protesters gather following the president's martial law declaration. Local media reported that a presidential declaration of martial law could significantly curtail freedom of speech, as the Constitution permits restrictions on press freedom under such circumstances. | AFP-JIJI

South Korea's main opposition Democratic Party leader Lee Jae-myung speaks to the media at the National Assembly after South Korean President Yoon Suk Yeol declared martial law. “There is no reason to declare martial law. We cannot let the military rule this country,” he said.
South Korea's main opposition Democratic Party leader Lee Jae-myung speaks to the media at the National Assembly after South Korean President Yoon Suk Yeol declared martial law. “There is no reason to declare martial law. We cannot let the military rule this country,” he said. | AFP-JIJI

A protester's sign reads
A protester's sign reads "Democracy will not surrender to Yoon Suk Yeol" | REUTERS

Placards calling for the president's impeachment are placed on a police vehicle
Placards calling for the president's impeachment are placed on a police vehicle | REUTERS

Police attempt to clear a path through a crowd of protesters for a military vehicle arriving at the National Assembly building on Tuesday night.
Police attempt to clear a path through a crowd of protesters for a military vehicle arriving at the National Assembly building on Tuesday night. | Chang W. Lee / The New York Times

Soldiers clash with protesters in an attempt to enter the National Assembly building.
Soldiers clash with protesters in an attempt to enter the National Assembly building. | AFP-JIJI

Military forces arrive at the National Assembly
Military forces arrive at the National Assembly | REUTERS

Police stand guard near the South Korean Presidential Office and the Defense Ministry in Seoul, following the president's announcement. Local news agencies report a heavy police presence and helicopters circling the skies.
Police stand guard near the South Korean Presidential Office and the Defense Ministry in Seoul, following the president's announcement. Local news agencies report a heavy police presence and helicopters circling the skies. | AFP-JIJI

South Korea's National Assembly Speaker Woo Won-shik called an emergency meeting on Wednesday morning, resulting in a resolution which passed unanimously, demanding the immediate lifting of martial law. By law, the president is obligated to honor the resolution.
South Korea's National Assembly Speaker Woo Won-shik called an emergency meeting on Wednesday morning, resulting in a resolution which passed unanimously, demanding the immediate lifting of martial law. By law, the president is obligated to honor the resolution. | AFP-JIJI

Soldiers withdraw from the National Assembly after lawmakers voted to block martial law earlier declared by the president. South Korea's National Assembly secretary general pledged to hold military members
Soldiers withdraw from the National Assembly after lawmakers voted to block martial law earlier declared by the president. South Korea's National Assembly secretary general pledged to hold military members "legally responsible" for any "physical damage and illegal acts" during President Yoon's brief martial law declaration, according to local broadcaster MBC. | Bloomberg

In the aftermath, National Assembly officials remove furniture barricades from the doors of the building.
In the aftermath, National Assembly officials remove furniture barricades from the doors of the building. | REUTERS

Furniture is piled up behind a door which was damaged when military forces broke into the National Assembly building.
Furniture is piled up behind a door which was damaged when military forces broke into the National Assembly building. | REUTERS

Following the night's chaos, people take part in a rally in Seoul to demand South Korean President Yoon Suk Yeol's removal from power.
Following the night's chaos, people take part in a rally in Seoul to demand South Korean President Yoon Suk Yeol's removal from power. | REUTERS

A rally demanding South Korean President Yoon Suk Yeol's impeachment, in the capital on Dec. 4. Yonhap news agency reports that around 40 South Korean lawmakers plan to propose a bill to impeach President Yoon Suk Yeol as early as Wednesday.
A rally demanding South Korean President Yoon Suk Yeol's impeachment, in the capital on Dec. 4. Yonhap news agency reports that around 40 South Korean lawmakers plan to propose a bill to impeach President Yoon Suk Yeol as early as Wednesday. | Reuters