I take tactical to mean something like "< 100 kilotons", meaning the damage would be much more limited than a large device. Those devices certainly exist. Wher

I take tactical to mean something like "< 100 kilotons", meaning the damage would be much more limited than a large device. Those devices certainly exist. Where it's somewhat plausible a nation could use one and face some retaliation that doesn't escalate into a global doomsday. Depends a lot on who/where/why, how much primary and collateral damage, and so on. You may be right that any use of any nuclear weapon turns into a global doomsday. It's hard to say unless it really happens. I'm often surprised that terrible war related incidents end up not escalating beyond the general region where they happened.