http://sethbaum.com/ac/2013_NuclearWar.pdf: Difficult reading.
https://www.quora.com/If-a-future-US-president-was-determined-to-use-nuclear-weapons-are-there-safeguards-to-ensure-he-she-cant-just-start-WWIII: Easy reading.
The links may not work, so you may have to type them in by hand.