Explain how and why the Cuban Missile Crisis Almost Resulted in WWII

The Cuban Missile crisis was perhaps the closest the world has gone to the point of all out nuclear war, and for 13 days in October the world was watching a dangerous game of ideological brinkmanship. The intensity of the situation was probably best described by Soviet General and Army Chief of Operations, Anatoly Gribkov as, "nuclear catastrophe was hanging by a thread ... and we weren't counting days or hours, but minutes."
The trigger for the Cuban Missile Crisis occurred when reconnaissance photos taken by the United States of Cuba showed a significant Soviet build-up of strategic missiles. …