True! But after the first nuclear attack, countries developed nuclear weapons for the sake of their own protection and deterrence. As far as winning a war is concerned no one can win it with nuke and at the end they just destroy the beautiful planet earth. Now countries are more interested in developing biological weapons which are even dangerous than nuke.
Biological weapons are having limited range, and if the recipient country is sufficiently prepared, then the impact will be limited. For example, if someone attacks the US with Anthrax, then the authorities will be able to limit the impact by vaccinating everyone against it.