On a night in October 1944, a German pilot and rocket expert by the same of Hans Zinsser was flying his Heinkel 111 twin engine bomber in twilight over northern Germany, close to the Baltic coast in the province of Mecklenburg. He was flying at twilight to avoid the Allied fighter aircraft that at that time had all but undisputed mastery of the skies over Germany. Little did he know that what he saw that night would be locked in the vaults of the highest classification of the United States government for several decades after the war. And he certainly could not have been aware of the fact when his testimony finally was declassified near the end of the millennium, that what he saw would require the history of the Second World War to be rewritten, or at the very minimum, severely scrutinized. His observations on that one night on that one flight resolve at a stroke some of the most pressing questions and mysteries concerning the end of the war. By the same token, what he saw raises many more mysteries and questions, affording a brief and frightening glimpse into the labyrinthine world of Nazi secret weapons development. His observations open a veritable Pandora's box of horrifying research the Third Reich was conducting, research far more horrendous in its scope and terrible promise than mere atomic bombs.
So, what exactly did the German pilot Hans Zinsser see on that night of October, 1944, as he flew his Heinkel bomber over the twilight skies of northern Germany? Something that, had he known it, would require the previous badly written Wagnerian libretto to be almost completely revised. His affidavit is contained in a military intelligence report of August 19, 1945, roll number A1007, filmed in 1973 at Maxwell Air Force Base in Alabama. Zinsser's statement is found on the last page of the report:
47. A man named ZINSSER, a Flak rocket expert, mentioned what he noticed one day: In the beginning of Oct, 1944 I flew from Ludwigslust (south of Lubeck), about 12 to 15 km from an atomic bomb test station, when I noticed a strong, bright illumination of the whole atmosphere, lasting about 2 seconds.
48. The clearly visible pressure wave escaped the approaching and following cloud formed by the explosion. This wave had a diameter of about 1 km when it became visible and the color of the cloud changed frequently. It became dotted after a short period of darkness with all sorts of light spots, which were, in contrast to normal explosions, of a pale blue color.
49. After about 10 seconds the sharp outlines of the explosion cloud disappeared, then the cloud began to take on a lighter color against the sky covered with a gray overcast. The diameter of the still visible pressure wave was at least 9000 meters while remaining visible for at least 15 seconds.
50. Personal observations of the colors of the explosion cloud found an almost blue-violet shade. During this manifestation reddishcolored rims were to be seen, changing to a dirty-like shade in very rapid succession.
51. The combustion was lightly felt from my observation plane in the form of pulling and pushing.
52. About one hour later I started with an He 111 from the A/D  at Ludwigslust and flew in an easterly direction. Shortly after the start I passed through the almost complete overcast (between 3000 and 4000 meter altitude). A cloud shaped like a mushroom with turbulent, billowing sections (at about 7000 meter altitude) stood, without any seeming connections, over the spot where the explosion took place. Strong electrical disturbances and the impossibility to continue radio communication as by lightning, turned up.
53. Because of the P-38s operating in the area Wittenberg- Mersburg 1 had to turn to the north but observed a better visibility at the bottom of the cloud where the explosion occurred (sic). Note: It does not seem very clear to me why these experiments took place in such crowded areas. 
In other words, a German pilot had observed the test of a weapon, having all the signatures of a nuclear bomb: electromagnetic pulse and resulting malfunction of his radio, mushroom cloud, continuing fire and combustion of nuclear material in the cloud and so on. And all this on territory clearly under German control, in October of 1944, fully eight months before the first American A-bomb test in New Mexico! Note the curious fact that Zinsser maintains that the test took place in a populated area. There is yet another curiosity to be observed in Zinsser's statement, one that his American interrogators either did not pursue, or, if they did pursue it, the results remain classified still: How did Zinsser know it was a test? The answer is obvious: Zinsser knew, because he was somehow involved, for clearly the Allies would not have control over a test site deep in Nazi Germany.
 "A/D" probably "aerodrome".
 The entire documentation of this report is as follows: "Investigations, Research, Developments and Practical Use of the German Atomic Bomb," A.P.I.U. (Ninth Air Force) 96/1945 APO 696, U S Army, 19 August 1945." The report is classified secret. Note that the report begins in no uncertain terms: "the following information was obtained from four German scientists: a chemist, two physical chemists, and a rocket specialist. All four men contributed a short story as to what they knew of the atomic bomb development." (Emphasis added). Note also the suggestive title of the report.