Yes. I know what it is. I just did not think it was used in Korea.
My grandfather spent much of his adult life in and out of VA hospitals because of mustard gas poisoning during WWI. He ate or drank something that was contaminated and had to have half his stomach removed.
He studied to be a jeweler and was able to make a living from his home repairing clocks and watches.
He never would speak of his war experience in France and Germany (he was infantry), but he suffered greatly from night terrors.