...an eventually made is way to Los Alamos where he drew a diagram of the German nuclear technology about which Heisenberg told him.
The American/British/Hungarian/German scientists found it amusing, and realized immediately it wasn't a bomb at all.
The Alsos mission found the reactor, which was basically along the lines of an early CANDU, and concluded it wouldn't work all that well.
Overall, the Americans found the German efforts laughable.
The Japanese also had a nuclear weapon program, but like Germany had nothing like the resources to see it through. The program that did succeed began as a British project, when impounded "Enemy Aliens" Otto Frisch and Rudolf Peierls, at British request, calculated the correct (more or less) critical mass of U-235 to make a bomb. In 1942, the British program was way ahead of the Americans, but certainly lacked the resources to see the matter through.
Bohr was stunned at the scale of the American effort, but was considered by Leslie Groves to be nothing more than a thorn in his side.
The debate has long been whether Heisenberg was incompetent to build a bomb or reactor, or whether he was deliberately sabotaging the effort.
I go with the former.
For the Nazis to build either a reactor or a bomb, they would need "Jewish Physics" which Heisenberg knew quite well but couldn't necessarily acknowledge, but he was never really the equivalent of Fermi, not even close. Although a great theoretician, Heisenberg lacked the experimental abilities that Fermi showed.
I saw Fermi's reactor last week at ORNL on the AMSE tour. It's a graphite machine, quite large, quite primitive, but it ran for 20 years.
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