Korea.

We have all been told ad nauseam how close the world came to World War Three/ Nuclear War with The Cuban Missile Crisis - yet it has taken the recent series Korea: The Forgotten War, In Colour to bring me to a realisation how that was in fact the closest the world has ever been to hurling nuclear weapons around. 
Caused purely by Communist N.Korea's invasion of the South - once the North started to lose - the Communist Chinese entered the conflict directly and Stalin supplied weaponry and 'advisors'.
President Truman based at least 26 nuclear weapons on Okinawa with full authorisation for their use in time of need.
How close communists have come to causing horror beyond the outer reaches of our belief - and on more than one occasion.
Today, even the 'rogue states' are unlikely to use these dreadful weapons knowing what the consequences will be.
What we have to fear today is terrorists with smuggling abilities getting hold of these cursed things.
How I wish they could be uninvented but they can't and so we must live with them as best we can.
Do remember though that their only usage in history was by one state which had them against another which did not!