Let me finish tonight with this.
Berlin, where President Obama spoke today, was for many of my generation - and for those older - the scariest of places.
I'm speaking about the 1960s... What historian Michael Bechloss called "The Crisis Years."
The crisis was the frightening chance that this planet of ours would burst into nuclear war, with the United States and the then-Soviet Union firing their vast arsenals of inter-continental ballistic missiles in one devastating conflagration that left the world destroyed, our atmosphere poisoned beyond the level of human survival.
Always in these "Crisis Years" it was the city of Berlin that could ignite this horror in our lifetimes, bringing with it the end of life, certainly as we can imagine it, or would want to recognize it.
Beginning with the defeat of Germany in the spring of 1945, the American, British and French had maintained an occupation in West Berlin, an island of freedom surrounded by the brutal dictatorship of East Germany, patrolled by the secret police - the Stasi - and garrisoned by 350,000 Soviet bloc troops.
West Berlin was in those early years of the 1960s, the "detonator cap" for a Third World War.
Why? Because if the Soviets had decided to grab it, the United States would have had just a sliver of the conventional military power to resist. Within hours we would have had to decide whether to yield the city up - along with the freedom of its residents - or use tactical nuclear weapons to ward off the attacking Red Army of 350,000 strong.
This is the prospect - the possibility that Kennedy would have to make this choice - that kept him worried day and night - that he would be the American president who would be forced to start a Third World War, a nuclear, world ending war.
This is what the Cuban Missile Crisis was about - not the island in the Caribbean where the Russians had placed offensive nuclear weapons - but what the Russians would do if we invaded it, the threat - made by Soviet leader Khrushchev in a letter to President Kennedy - that he would respond by taking Berlin - thereby setting up the nuclear tripwire, starting the countdown to a Third World War.
This is what Berlin meant in the years 1961 and 1962. It's why Kennedy said when he heard the Russians had put up the Berlin Wall: "Better a wall than a war."
It's why the people of West Berlin were so exuberant when Kennedy came to visit in June 1963 - fifty years next week. It's because the American people were determined to stand their ground in defending them.
More than that, it was our country's statement to the rising Third World, especially the new-independent countries of Africa that this was the choice they faced in building their own societies - a free West Berlin - or a society that needed walls to keep its people in.
"There are many people in the world who really don't understand, or say they don't, what is the great issue between the free world and the Communist world," said Kennedy. "Let them come to Berlin. There are some who say that communism is the wave of the future. Let them come to Berlin."
Jack Kennedy's speech in West Berlin was for all these reasons the finest statement of the Cold War - what the conflict was about, what the stakes were, what the rising new world should learn from it.
Nothing in my life was so stirring historically than to stand on the Eastern side of the Brandenburg Gate back in 1989 and ask a still-captive East German what freedom meant to him - and have him respond in German that it was the ability to talk openly with an American reporter: Me