President Yoon Suk Yeol on Thursday called for unity as South Korea commemorates the 43rd anniversary of the clampdown on pro-democracy protests in Gwangju, a city located some 330 kilometers south of Seoul.

The civilian-led protests against the military rule of former president and dictator Chun Doo-hwan were met with tanks, bullets and arrests. In the course of 10 days, Chun’s troops crushed the wave of protests, at least 165 were believed to have been killed and thousands more injured. As there is no official figure, the true death toll remains unknown to this day.

At Thursday’s memorial ceremony, Yoon expressed his “deepest respect and admiration” for the people of Gwangju who fell to their deaths fighting for democracy.

"We gather here today to remember the resistance of May that saved our democracy with blood and sacrifice,” he said.

“Democracy in this country wasn’t built in a day. We owe it to the bravery and dedication of our democracy fighters. And Gwangju was on the very forefront of the battle for democracy, freedom and human rights.”

He said that to uphold the spirit of May, the country must “have the courage to boldly combat all the challenges that jeopardize freedom and democracy” and “not forget the lessons of history.”

He made a plea for unity: “Under the May spirit, we are one.”

In a symbolic move, the president walked with the bereaved mothers who lost their children to the Gwangju crackdown to the gate of the national cemetery, where the victims are laid to rest. He thanked them for their courage and pledged to stand with them.

“I can’t begin to fathom the depths of your pains,” he was quoted as telling one of the mothers. He said that their children were “unable to return home because of the country’s forces” in an admission of state violence.

Leaders on both sides of the political aisle paid tribute to those killed in the brutal crackdown at the ceremony attended by more than half of the National Assembly members.

“All of us owe it to the people who stood up for democracy and peace that May,” Rep. Kim Gi-hyeon, the ruling People Power Party chair, said at the ceremony. “How far we have come since the Gwangju movement proves that democracy is worth fighting for.”

Rep. Lee Jae-myung, the chair of the Democratic Party of Korea, pushed for making revisions to the Constitution to include preambles honoring the Gwangju protests.

“There should be no place for partisanship in enshrining the spirit of the Gwangju movement in the Constitution,” he said, calling on the president to follow through with his earlier promise to do so. He said that without Constitutionalizing the democracy protests, the president’s words would be “hollow.”

On the anniversary’s eve, Chun Woo-won, the grandson of the military dictator who seized power in 1979 through a coup, attended a remembrance event held at the national cemetery. “I’m honored to be here,” he was heard on tape telling reporters.

The 27-year-old is the first in the presidential family to publicly apologize to the Gwangju victims and their families. In his visit to Gwangju in March, he described the crackdown on protesters under his grandfather’s rule as a “massacre.”