Re: U-Boats Were the Key
Ultra had an enormous effect, Polish. There is simply no doubt about that, yet alone it would not have been enough to stop a hundred or more U-boats in the N. Atlantic had the Germans been able to deploy that many. The main use of Ultra was to allow convoys to avoid known concentrations of U-boats. With sufficient numbers, the convoys would have been found, Ultra or no Ultra. And if found, those convoys would have been decimated.
--Pistolenschutze (Pistol Shooter)