As World War II raged, both sides sought an edge, especially in the early years when it could have gone either way. Scientists were close to figuring out how to make an atomic bomb, and whoever had it first would have an unsurmountable edge. The United States did develop the bomb, and used it in August of 1945, which ended the war with Japan.
The Germans were very close, and there is some evidence that they may have gone further than many realized at the time. There are quotes from people who say they saw a nuclear test in 1944 by the Germans.
A German, Hans Zinsser said he saw “A cloud shaped like a mushroom with turbulent, billowing sections (at about 7000 meters) stood, without any seeming connections over the spot where the explosion took place.”
He said there were also electrical disturbances at the time that made radio communication impossible.
The German pilot said those words in an article published by the Daily Mail of London. He was doing test flights at the time, and what he described does indeed sound like an atomic bomb blast.
The whole thing could have gone in a drastically different direction though. In 1938 a German scientist, Otto Hahn, discovered nuclear fission. That is the essential ingredient to making an atomic bomb.
The Germans then began a project to develop the bomb. They were able to build nuclear reactors, called uranium machines. They did not have enough of what is known as “heavy water,” and that is what kept them from winning the nuclear race.
It severely limited Germany’s ability to continue the program when the heavy water from Norway was shut off.
An article published by PBS, written by Mark Walker, suggests that in the final months of the war, Germany did test a nuclear bomb. Another German pilot, and an Italian advisor, also saw the blast.
One thing that may have also hurt the program, was that in 1942 Hitler separated the nuclear project from the military. The project became more concerned about developing alternative energy sources than specifically making a bomb. It was not until later in the war that German again desperately sought one as the tide of the war turned against them.
Small decisions, like separating the program from the military, and the loss of a heavy water supply, hindered Germany’s efforts to make an atomic bomb. Even so, it is fairly clear that they did manage to make one bomb, which was tested. Several witnesses say they saw the explosion that had a mushroom cloud, and that it had all the signs of a nuclear blast.
So based on those witnesses, we can be fairly certain that Germany did develop a bomb, perhaps even before the United States did. But by the time Germany developed the one test, it was too late to change the tide of the war, and probably too late to build one that they could actually use.