This is pretty amazing. It’s a Scientific American Article from 1939 describing the splitting of the atom. It was written just after Einstien had written his famous letter to F.D.R and before the initiation of the Manhattan Project, yet it is obvious that scientists were well aware of the potential uses of atomic fission:

It may or may not be significant that, since early spring, no accounts of research on nuclear fission have been heard from Germany — not even from discoverer Hahn. It is not unlikely that the German government, spotting a potentially powerful weapon of war, has imposed military secrecy on all recent German investigations. A large concentration of isotope 235, subjected to neutron bombardment, might conceivably blow up all London or Paris.

Two Elements For One

The Most Important Scientific Discovery of the Present Year is also the Biggest Explosion in Atomic History … Splitting the Uranium Atom

THE Fifth Washington Conference on Theoretical Physics was sitting in solemn conclave when the news broke. Professor Nils Bohr of Princeton and Professor Enrico Fermi of Columbia rose to open the meeting with an account of some research going on in a Berlin laboratory.
Professors Bohr and Fermi are Nobel Prize winners both, and their names are as well known to scientists as Toscaninni’s is to music lovers. The Conference therefore expected something extra special. They weren’t disappointed.

It was January 26, 1939. A few wees before, at the Kaiser Wilhelm Institute in Berlin, Dr. Otto Hahn, a distinguished German physicist, had obtained an utterly unexpected result from some more or less routine experiments. Following the original example of Professor Fermi, Dr. Hahn and his co-worker, F. Strassmann, had for many months been bombarding uranium with neutrons and studying the debris left by this atomic warfare.

It would not have surprised them at all to find radium as one of the products. In fact, they had done so before, or thought they had. Radium and uranium are near neighbors in the table of elements, and it is nothing new for scientists to transform one element into another close to it in weight and electric charge.

But it was news, and big news, to discover barium among the debris — barium, which is only a little more than half as heavy as uranium. It meant that the neutron bullets had succeeded not merely in knocking a few chips off the old block, but in blowing the whole atom asunder with a terrific explosion.