This was an absolutely terrifying interview with Theodore Postol regarding just how littler response time Russia has in case of a nuclear strike. A decision basically has to be made under 5 minutes, which rules out any sort of a centralized response coordinated at the top. The people in charge of the weapons basically have to make a call immediately whether they end the world or not.

https://www.youtube.com/watch?v=RH7LT1bIdpY