An interesting tidbit I haven't hear before, which casts the event into a completely different light (not sure how accurate):

I decided that the computer made a misidentification, I let myself distrust it, all because I was the one who designed it. Only its creator can be allowed liberties like that. I knew every piece of code better than the computer did.

Petrov was not just a random soldier thrust into a critical situation and possibly out of his depth, he was an expert. He had a B.Sc./M.Sc. in Computer Science and Engineering, then he had a two-year (!) training course of information processing on nuclear watch, and he participated in the design and testing of the target identification system in question. I cannot imagine a more qualified person in this situation, and I doubt that the US procedures come anywhere close.

Another quote:

The infamous red button was not actually connected to anything. The wires underneath were cut. I had to decide what and how to report to my superiors. I sent my assistant to report a false alarm.