As an ex south korean army (mandatory service), our neighbor in the north still think chemical weapon an effective asymmetrical weapon against us because our small piece of land won't really allow any mobility based modern warfare. There are outposts throughout all the borderline.

We do quite a lot of training to protect against chemical attacks and also the protective respiration devices are included for every soldiers. The most probable attack against us will begin with spreading chemical gas on air to crush the first defense line in the borderline.

If situation become really bad and raw - killing all the civilians - chemical weapon would still be a very effective weapon I think.