The response time of a back-up force supporting ground movements of nuclear weapons is 15 minutes. This is probably because nuclear weapons are kept on hair-trigger alert – this means that the back-up force could strike within 15 minutes once a decision to support ground movement has been made. The response time is just sufficient enough so that it could safeguard the command from unauthorized or accidental launches because once a nuclear weapon has been launched, it cannot be recalled.
15 minutes was always the norm when it comes to response time. Hillary Clinton was subjected to different negative comments when she discussed that the response time for back-up force to launch nuclear weapons should only be four minutes. This means that once the President gives out his order to launch the nuclear weapon, there will only be a window of four minutes and not fifteen minutes.