Did the Allies' attacks on Germany's heavy water supply lead to any reevaluation of its nuclear goals?

Question

It is well-known that throughout much of WWII the Allies made persistent attacks on Norsk Hydro's Vermork heavy-water plant, and on the transportation of heavy water from there, up until the point where there was nothing more to be done in that respect. This might seem to signal that the Allies considered Germany's nuclear technology to be a major threat - more so, in fact, than the Germans themselves thought it could be. Is there any evidence that German intelligence and policy-makers made this connection, and if so, whether that led to any reevaluation of the feasibility and potential of that technology? Was there a person or faction arguing, in effect, "our enemies are clearly concerned by this, so perhaps we are underestimating its potential" or "perhaps our enemies' concern in this matter is because they have found it to be more feasible than we think?"

The question I have here is about the German analysis of the Allies' actions and their motives.

Answer 1

Answering this needs some context. Like quite a few German technological projects of the WWII era, the German nuclear project was ill-founded and under-resourced. The importance of heavy water was that it could be used as a moderator for a nuclear reactor, which could be used to make plutonium.

The German project was well aware of these things, but had failed to appreciate the difference between the fast-neutron reactions that you need for an atomic bomb and the slow-neutron reactions of a reactor. All of this is quite clear from the Farm Hall transcripts published by Jeremy Bernstein in Hitler's Uranium Club.

The various members of the project had tried to get resources, but had been self-sabotaging. Senior academics had great prestige in inter-war Germany, and the project members had not been obliged to learn how to explain the basics of their knowledge to people less knowledgeable than their doctoral students. Nor were they good at admitting to themselves, or each other, what they didn't know. So they turned down offers of large resources, saying that the knowledge to make use of them was not yet available. Two years later, it was clearly pointless to ask for huge resources, so they didn't.

By contrast, the Manhattan Project had been set up by people who know how to communicate with academics, and its scientific leader, Oppenheimer, had been chosen for his unusual gifts in getting physicists to work together. It also had Enrico Fermi, who was gifted in both theoretical and experimental physics, and was one of the best engineers ever to win a Nobel Prize.

One outcome of all this was that as of August 1945, when the German physicists detained at Farm Hall learned of the bombing of Hiroshima, Werner Heisenberg, the head of the German project, while aware of the concept of a critical mass, had no real idea of its size, and sat around talking about it, rather than attempting to calculate it. He was a quantum mechanics theoretician, and a gifted one, but not a practical man or an organiser of teams.

The German Armaments minister, Speer, does refer to the German nuclear project in Inside the Third Reich, saying that he'd given up on it by mid-1943, when he released the stocks of uranium metal to be used in anti-tank ammunition. The physicists had a strong personal motive to keep it going on a small scale, in that it was work they were interested in and relatively safe. Getting conscripted into the army and sent to the Eastern Front was always a prospect for them, and was close to a death sentence.

Their post-war claims that they deliberately withheld atomic bombs from Hitler don't stand up, although they were doubtless good for their self-esteem. They didn't do the right things at the start, and never had the resources to catch up.

Answer 2

1. Nobody knew then for sure, that heavy water can be used for nuke. Even more, for the current state of technologies, really, it was useless. But some scientists on the West were not sure about that(and it was a mistake!). Nobody wanted to take risks and that resulted in these attacks.
   But why a successful attack at a mediocre factory should mean super-great importance of its production? These times the use of heavy water was for science only.
   And the possibility of success of an attack is accidental. And nobody uses Bayes' formulas for reverse evaluation of usability. That would mean that the enemy is many times more clever than you and the struggle has no sense at all. And Germans considered their enemies as beings of lower order and wouldn't learn from them.
   And even if they would accidentally start to think about that, Germans couldn't get the proof for use of heavy water, because such proof simply didn't and couldn't exist then.

2. AFAIK, Hitler never canceled his order about no serious investments in weapons that will appear in more than year. They really had no resources for that. Even for USA the nuke program was very expensive. And if Americans knew the real level of the nuke "projects" of Germany, it would not start for this time. According to https://en.wikipedia.org/wiki/German_nuclear_weapon_project, practically no real nuclear program existed in Germany. They were many years behind. And even much more serious information wouldn't lead to improvement, for to understand the problem there should be a person capable to do it. No one existed already. To do serious science you need at least relative freedom of thought. With Einstein works ban, there was not any. In Russia ideologists also wanted to ban quantum physics and Theory of Relativity. But Kurchatov wrote to Stalin, asking, if they really want to have an A-bomb? Stalin did, and ideologists were stopped. And nuclear physics in USSR was free of ideology. There was not such figure as Kurchatov in Germany.

3. What is interesting, if Allies would intentionally desinform Germans about great use of heavy water for nuclear weapon, Germany could lose a pair of months earlier, for they couldn't ignore such threat from the West. But as they themselves were not sure about the real use of heavy water, they were afraid to HELP Germans with that information.