But this is the whole concept of the "nuclear triad" -- bombers, land-based missiles and submarine-based missiles. It would be nearly impossible to stage an att

But this is the whole concept of the "nuclear triad" -- bombers, land-based missiles and submarine-based missiles. It would be nearly impossible to stage an attack so stealthily that all three legs of the triad would be unable to respond. It's like keeping backups of your data in multiple places and/or on multiple media, a method of assuring recoverability when part of the solution inevitably fails.