Imagine you're a nuclear physicist in 1947. You've just seen the devastating and horrifying effects of the atomic bomb. Then an Army general asks you to work at a secret government lab applying newly harnessed Atomic Energy to a new class of super-weapons because.. um.. Ruskies are coming! While you still regretting building the first atomic bombs and and giving Man the ability to fully destroy itself and the whole world, are Russians a good enough motivation to invent things even more awesomely powerful? Probably not. So what kind of threat would get a bunch of new-found passivists back into the lab?