Protests outside South Korea's parliament after President Yoon Suk ...
Martial law comes after wrangling over budget billpublished at 14:31 Greenwich Mean Time14:31 GMT
Jake KwonReporting from Seoul
Yoon has been a lame duck president since the latest general election when the opposition won a landslide in parliament.
He was not able to pass the laws he wanted, instead, he was reduced to vetoing desperately any bills that the opposition had been passing.
Yoon is also mired in several scandals, mainly one around his wife, who is accused of corruption. She is also accused of influence peddling. The opposition has been trying to launch a special investigation against her.
This week, the opposition slashed budgets that the government and ruling party had put forward - and the budget bill cannot be vetoed.
In the same week, the opposition is moving to impeach cabinet members, mainly the head of the government audit agency, for failing to investigate the first lady.
Yoon has gone for the nuclear option - he claims it is to restore order when "anti-state" forces he says are trying to paralyse the country.