The president of South Korea had declared martial law under patently false premises in a transparent attempt to suppress political opposition. Fortunately, it has been rescinded after members of the South Korean parliament who were present unanimously voted against the declaration of martial law, despite obstruction by the police and the military.
Given the parallels between the current South Korean president and the former and future president of the United States, it is troubling to think about the next four years. This is especially so given precedent; if a mob of civilians failed to install a dictatorship, maybe the military and federal law enforcement under direct and clear orders could do the job?
It is fortunate for South Korea that the parliamentary vote against the declaration of martial law was unanimous. I would not hope for something as decisive from the US Congress; such a vote will not be unanimous, and there may in fact be enough Republican votes against it to freeze Congress into inaction. On the other hand, while federal law enforcement was compliant enough to teargas protesters for a photo-op, the military had resisted efforts to use them in direct suppression of protests. This may be a vain hope; it is not clear what will happen if there is a clear and direct presidential order.
The most horrifying aspect of this all when thinking about potential martial law in the context of the United States is that under the current Supreme Court, there would be absolutely no criminal liability for the president. No matter how false the premises may be or how the military might be used, there would be no question that this would be an official act by the president.