I mean, North Korea isn't so stupid as to advertise all of their artillery positions. And they certainly didn't place them all within a 5 mile band.

But, the main problem is that China, Russia, and South Korea(Japan Probably too) would VEHEMENTLY oppose using a nuke right in their back yard.

On top of this, Tactical Nuclear weapons have never publicly been used. This would be opening a whole new pandora's box. If you're allowed to use 100 "small, tactical" nukes... then what's to stop somebody from using 10 "medium, tactical" nukes instead. Or 2 "big" nuke. Or 1 "gigantic" nuke.

The reason nuclear bombs are not used, is because the feared domino effect. If the USA starts using tactical nukes... what's to stop Pakistan from using them. Or India. Or China. Or Russia. Or Iran. Or Israel. Nothing at all, is the answer.

If the USA was the only country that has the ability to use tactical nukes(like it was the only country with nukes, during WW2)... they could be used without global repercussions. But, as it stands, many nations are capable of manufacturing, or procuring tactical nuclear weapons.

It's a pandora's box that is simply not worth opening. Conventional weapons can be used for most scenarios, where tactical nukes are used. And plus, the use of high altitude EMPs(which are similar to tactical nukes), seems much more likely than the use of tactical nukes themselves.