The Hiroshima shadows.

[vorlon13]

I'm not sure when for sure, but when Roosevelt told Stalin we had a new weapon of unusual power, Stalin already knew about the atomic bomb and had for long enough to already have started efforts to build a Soviet version.. If Stalin were to have been advised we were contemplating nuking Berlin, he would have been all over himself to help. Clearing troops, secreting diagnostic and test samples in the blast zone, redoubling spying efforts on the technology, anything to gather more intel on the device.

Also, he would have soon learned stealing the device wasn't feasible, but he would have made absolutely sure before gave up the idea.