So the minute a 'Small Nuke' is used, we should just respond with the biggest nuke. In any case the U.S. has stated that it won't do that unless it was a close

So the minute a 'Small Nuke' is used, we should just respond with the biggest nuke. In any case the U.S. has stated that it won't do that unless it was a close strike against a very close ally (NATO partner or similar, or their deployed units). Most likely won't reciprocate to a nuclear strike against just Ukraine (provided it were of "limited" scope such as a warning or sequence of tactical shots).