What is a tactical nuclear weapon - and could they be used in Ukraine?

Tactical nuclear weapons don't exist in the sense that nuclear use on a battlefield cannot be confined to the tactical level of warfare. They are better described as 'low yield nuclear weapons' of between one and 30 kilotons. They are much smaller than strategic nuclear weapons and the military effects on the ground in terms of destructive power would range only between one to three kilometres, with the radioactive fallout depending on burst-height and the weather. In Ukraine, this would likely contaminate Russian territory also and there are no military targets that would have to be destroyed by these weapons as conventional means could be used instead."