His tweet is alluding to nuclear deterrence. https://en.wikipedia.org/wiki/Deterrence_theory https://en.wikipedia.org/wiki/Deterrence_theory Doesn't do squat a

His tweet is alluding to nuclear deterrence. https://en.wikipedia.org/wiki/Deterrence_theory https://en.wikipedia.org/wiki/Deterrence_theory Doesn't do squat against terrorists though, which is the most prominent threat (as far as the government sees it) of the 21st century.