[TinyTim]

Ow

But there is such thing as tactical nuke.

They are typically very small yield (for a nuke) weapons.
The smallest nuclear weapon I know of that was detonated was code named Ranger Able and yielded "only" 1 kiloton. It was dropped by a B29 over New Mexico. I'm not sure of the year.

Tactical nuclear weapon with smallest yield was a Davy Crockett fission device (recoilless gun delivery method) with a yield equivalent to about 20 tons TNT, tested on July 7 1962 during Little Feller nuclear test. Russian suitcase fission devices (RA-115) are believed to be of similar dimensions and yield.

Davy Crockett:



Tactical nuclear weapons are usually delivered by tactical and not strategical means - artilery/mortar shell, tactical fighter bomber, SRBM, torpedo, SAM missile, air to air missile...