Nuclear deterrence is relevant only to nations with nuclear capability, and not to the religious fanatics referred to by Bruce Kent (Letters, 13 December) who … “are only too ready to move into their imagined paradise”. This description does not apply, for example, to Kim Jong-un or Vladimir Putin, who have earthly power in mind and would be delighted if other world leaders abandoned this form of defence – terrible, but necessary in the world of today – for the people for whose safety they are responsible. Any rational person would be eternally grateful if nuclear weapons could be abolished forever, but the genie is out of the bottle. It cannot be put back in again, and well-meaning unilateral renunciation would only play into the hands of the aggressive and