If the US was ICBM attacked why do you think they would not sound the civil defense alert on everything as soon as they confirmed our launch?
Why I say confirmed our launch is there have been at least one close call on each side. One I remember the details of one was the USSR Officer in charge, Stanislav Petrov, over-rode the information from the radar and 40 years ago, on 26 September 1983, he saved from potential nuclear disaster....