In first 20 minutes of the documentary The Fog of War Robert McNamara goes over the Cuban missile crisis in detail. Even he admits it came down to luck.

His meeting with Cuba in the 90s and the new information presented that McNamara didn’t have during the crisis was especially sobering. McNamara ended the meeting early because he was “unprepared” to learn there were missiles already operational and authorization was already granted to launch if the Cuban build sites were struck.