John brought up an interesting point today. Now, the point is from a book he can't find by an author he can't remember, but the point rings true - Nuclear weapons had nothing to do with the relative peace that followed WWII; rather, it was the world leader's experience of the Second World War that encouraged them not to engage in anything similar.
This has its merits - Eisenhower, Khrushchev, and De Gaulle come to mind. Generals, especially, who succeeded in the key area of "not having major foreign wars". They came close - Eisenhower had Korea, Khrushchev fell out of favor post-Cuban Missile Crisis, and de Gaulle both came to power through a coup and then ended a colonial war in Algeria. They led nations in conflicts, but they were always about keeping it contained, keeping it manageable, and about ending it. It's a valuable experience, and their respective roles in WWII no doubt had a serious effect on the outcome.
The trick with relying on memory as the reason no major powers went to war against each other is that memory fades, and people with the memories get old and die. Currently, the united states is on it's second "Baby Boomer" president, and seems ready to elect a third. Putin was born in 1952, and to continue the parallel Sarkozy was born in 1955. These people have no living memory of the second world war, and to be fair, they have no memory of Hiroshima or Nagasaki as well.
They do, however, have a lifetime of fear instilled in them over the prospect of a nuclear war. The cold war left that as a solid legacy (what is the point of 'duck and cover' if not to instill fear?), and they had the actual devastation of Hiroshima and Nagasaki to look back on. The atomic bomb, born of the horrors of WWII, found it's place as a lasting reminder of the exceedingly high costs of war between great powers. The living memory of those first leaders is not to be discredited, (surely, if they had wanted to use the bomb they would have), but the bomb itself, that intense amount of otherworldly power in such a small capsule, will last, and will endure, as the ever-present threat and the lesson learned. Perhaps the bomb did not establish the peace - the bomb certainly secured it.