I specialized in the Soviet Union during the Cold War, and I would have to agree that all the evidence points to the first point where there would be long-lasting, widespread European peace would be immediately after World War 2. My personal theory about this is that WW2 did what WW1 was supposed to do, and be the War to End All Wars (if you're a European anyway) because we haven't had a major war in Europe since then. My definition of "major war" is one sovereign nation declaring war or militarily invading another sovereign nation using their uniformed armed forces.

Most would cite the formation of the United Nations in late 1945 as the pivotal moment when another European war was set in policy as something to be avoided.