So a few times in the news, it’s been covered that the USAAF targeted ball bearing plants- and the effects on production was minor.
Is there any evidence that this was known at the time?
On one hand, it makes some sense that it was not effective, since ball bearings are pretty easy to produce and import- so getting them from other controlled territories or countries willing to take nazi money isn’t that hard.
On the other hand- could have that been deduced at the time?
I don’t think so. Also James Holland Big week claimed the Germans had to use lower quality flat bearing which let to accidents with eg German airplanes killing pilots. Sadly the Swedish and Swiss Governments were not the “clean people” they claimed to be after the war.