Tartare, yes, known as warnings and indicators against which appropriate responses could be made. The only snag was Red didn't have the same book.
One of the better, but by no means absolute, was streams of missiles spotted by BMEWS. Slightly better was an observed nuclear detonation. In the SAC Command Post was a NUDETS lamp which would light if there was a nuclear detonation in the continental USA.
There were instances where there were no indicators or there were but they were no recognised or not reacted to.