This question is too basic; it can be definitively answered by a single link to the relevant topic on Wikipedia or another standard reference source. If you are instead questioning the correctness of a reference source, please edit the post to supply a link and explain what you find unclear, or why you believe it to be wrong or incomplete.
Closed 5 years ago.
I have heard historians claim that enemies' ball bearing factory locations were a coveted piece of intelligence. I have also heard that big money industry for both the allies and axis super powers colluded to NOT bomb each others' ball bearing factories because it would "end the war too soon". These are some narrative fragments that have always left me curious about the significance of ball bearings to industry and particularly war industry. Were they a high-leverage pinch-point in the type of supply chain necessary to build a modern military?