Minutes after South Korea’s president, Yoon Suk Yeol, declared martial law on Tuesday night through a decree, Lee Jae-myung, the main opposition leader, called on his supporters and members of his party to gather at the National Assembly.

       Mr. Lee wanted lawmakers to pass a binding resolution to nullify the martial law decree, and he warned that the president might order the military to arrest them to stop the vote.

       “The people should defend this nation,” Mr. Lee said during a live broadcast on social media on his way to the National Assembly in Seoul. “Please come to the National Assembly.” Thousands did.

       Here is what to know about Mr. Lee.

       From sweatshop worker to politician Mr. Lee, whose parents cleaned public toilets for a living, spent his teenage years as a sweatshop worker, nearly losing his left hand.

       Now 60, he worked for two decades as a labor lawyer defending workers’ rights before entering politics in the mid-2000s and rising up the ranks of the Democratic Party of Korea, becoming a mayor and then a provincial governor.

       In April 2020, the Democrats won a supermajority in the National Assembly lasting four years.

       Mr. Lee ran for the presidency in 2022, pushing for social programs that were widely popular among his supporters, like universal basic income and personal loans subsidized and backed by the national government.

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