The airplane, the surprise by airplane, and the equipment of the planes with radar—which in my opinion is, next to the atomic bomb, the decisive war-winning invention of the Anglo-Americans—brought about the collapse of U-boat warfare. The U-boats were forced under water, for they could not maintain their position on the surface at all. Not only were they located when the airplane spotted them, but this radar instrument actually located them up to 60 nautical miles away, beyond the range of sight, during the day and at night. Of course, this necessity of staying under water was impossible for the old U-boats, for they had to surface at least in order to recharge their batteries. This development forced me, therefore, to have the old U-boats equipped with the so-called “Schnorchel,” and to build up an entirely new U-boat force which could stay under water and which could travel from Germany to Japan, for example, without surfacing at all. It is evident, therefore, that I was in an increasingly dangerous situation.
FLOTTENRICHTER KRANZBÜHLER: Admiral, in order to characterize this situation I want to call your attention to your war diary of this time. This will have the Number Dönitz-18, reproduced on Page 32, Volume I. I want to read only the contents of the entries from the 2nd until the 14th of September, Page 32:
“On 2 September U-256 surprised and bombed by aircraft; unfit for sailing and diving;
“On 3 September aircraft sights U-boat;
“On 4 September U-756 has not reported despite request since 1 September when near convoy; presumed lost.
“On 5 September aircraft sights U-boat;
“On 6 September U-705 probably lost because of enemy aircraft attack;
“On 7 September U-130 bombed by Boeing bomber;
“On 8 September U-202 attacked by aircraft in Bay of Biscay.
“On 9 September...”