The industry union's representatives gathered for an emergency meeting just a few hours after President Yoon Suk-Yeol declared martial law on Tuesday evening local time.
Everyone was incredibly upset and determined that we had to take strong action, says Kim Han-Ju.
Power to influence
The response was a four-hour strike on Thursday and Friday. On Saturday, all members are urged to refuse overtime.
According to Kim Han-Ju, 45,000 workers at Hyundai and 10,000 at General Motors are on strike. The union has a total of 190,000 members.
This is a warning to the president where we want to say: We saw what you did. We organize companies that account for the majority of South Korea's exports, steel and freight. We are like IF Metall in Sweden and have the power to influence society, says Kim Han-Ju.
The days that followed have been hectic, says the union's head of international affairs. At their office in central Seoul, an employee walks by with a toothbrush in hand.
We sleep, eat, and shower here. We are here all the time except when we are out demonstrating, says Chong Hyewon.
On Saturday, a vote will be held in the National Assembly on whether the president should be impeached.
If he does not choose to resign, we will propose a full-scale strike from next Wednesday.
"Rights are being taken away from us"
According to Kim Han-Ju, it is a reasonable response to the martial law.
We have not had military laws since South Korea was a dictatorship in the 1980s. It means we cannot demonstrate, it prevents the press from working freely, all our rights are being taken away from us, says Kim Han-Ju.
Like many others in South Korea, he is worried that the president will declare a new martial law.
If he feels cornered, he could do it again. That's why we think it's incredibly important and urgent that he resigns as soon as possible.
The country's largest trade union umbrella organization KCTU, which is organizing the strike, has sent the same message to over one million members, including industrial union members.
Their office is just a stone's throw from KMWU. Outside, employees are handing out buttons in different colors with the message: "The people will save the country from destruction".
