Could Germany or Japan hide a 1945 nuclear test?

Could Germany or Japan have detonated a nuclear weapon in 1945 without the Allies detecting it?

No; Allied human intelligence, signals intelligence, reconnaissance, and knowledge of enemy unit locations made a secret test implausible.

The panel rejects the possibility of a concealed test, citing Allied human intelligence, signals intelligence, and aerial reconnaissance. Germany's collapsing command system provides the example: Allied officers could sometimes locate German units more accurately than the Germans trying to contact them. One surrender anecdote places a formation about twenty miles from where its own side thought it was. Some formations also retained divisional labels after casualties had reduced them to company strength.