Answer: The effects of nuclear weapons. Credible nuclear deterrence, debunking "disarm or be annihilated". Realistic effects and credible nuclear weapon capabilities for deterring or stopping aggressive invasions and attacks which could escalate into major conventional or nuclear wars.
Classified Government weapons and war exaggeration secrets: the problem
Hitler's Mein Kampf, 1925: "The great masses of the people will more easily fall victim to a big lie than to a small one."
"I remember very vividly, a few months after the famous pacifist resolution at the Oxford Union visiting Germany and having a talk with a prominent leader of the young Nazis. He was asking about this pacifist motion, and I tried to explain it to him. There was an ugly gleam in his eye when he said, 'The fact is that you English are soft'. Then I realized that the world enemies of peace might be the pacifists."