As World War II was winding down and the Third Reich was in its final days, British and U.S. military experts began a feverish hunt for military photographic archives deemed to be of enormous significance.
Worried that the collected reconnaissance photos of the German air force might fall into Soviet hands, the British and Americans formed special units to search for the photo library of the Luftwaffe. The code name of the secret operation was Dick Tracy.
Operation Tracy finally found its photos in a haystack near Bad Reichenhall in Bavaria.
In late April 1945, while rummaging through a barn, investigators found dozens of metal canisters containing about 800,000 aerial photos.
The Americans, as one witness later recounted, were "delighted" with the "brilliant clarity" of the photos and the fact that three-quarters of them documented Soviet territory all the way to the Caspian Sea.
The photos, from the Luftwaffe's main photo division in Berlin, were taken to the War Department in Washington. But the collection was not quite complete. But 100 photos had been taken by the Berlin photo division's last commander, Col. Hans Ruef, who hid them in his home in Gmund, on Lake Tegern.
Only recently, 12 years after Ruef's death, his daughter, writer Ingeborg Mnzing, found the photographic record among her father's possessions. The discovery was no accident.
Ms. Mnzing had not always been particularly interested in her father's military career. But television reports about the Persian Gulf war sparked her interest and induced her to comb through (( her father's belongings.
When television reporters talked about the amazing accuracy of the U.S. bombs, she recalled that her father used to boast of the precision of German reconnaissance photos and the careful targeting of German warplanes.
Most of the photos found by Ms. Mnzing were taken during the Germans' war against the Soviet Union, judging by various evidence and letters left by Mr. Ruef. They reveal the perfection -- unmatched by any other country in the world at that time -- which Luftwaffe aerial reconnaissance allowed German bombers to attain.
Photos from the Ruef collection show how, in August 1941, German bombers hit -- precisely in the middle -- a dam on the Dnieper River near Saporoshiye in the Ukraine.
Another series of pictures taken in July 1941 shows how military officials in Moscow prepared the area around the Kremlin for an expected German aerial attack: They painted the roofs of some buildings to camouflage them, and constructed dummy structures to draw German fire.
The speed with which the Luftwaffe worked -- both reconnaissance flights and bombers -- is shown by photos taken on Aug. 4, 1941. On that day, German Stukas flying near Smolensk managed within a few hours to destroy some 2,500 Soviet army planes on the ground, virtually unopposed.
The photos show why only small numbers of Soviet soldiers were able to escape the Wehrmacht attackers in the Smolensk region. Mr. Ruef, then chief photo officer in the high command of the 2nd Air Fleet, under Field Marshal Albert Kesselring, wrote to his wife, Ilse, in Bavaria that "the air photos are enough to make your blood curdle."
The photo cache uncovered by Ms. Mnzing also sheds light on another aspect of German aviation history -- the fascinating life of Ruef, a pioneer in civil aerial surveying.
He was born in Freiburg in 1894, the same year as Sidney Cotton, known as the father of British photo intelligence.
Ruef, who was barely out of high school when he was trained as a pilot to fight in World War I, had a second interest that prepared him perfectly for a career in aerial reconnaissance and surveying: He was as passionate about photography as he was about flying.
Between the world wars he used these skills in the civilian world, doing aerial surveys for companies, ministries and universities.
Ruef flew all over Central Europe, taking photos of cities, rivers and the Alps. He refined the methods of a still new measurement technique known as photogrammetry -- of fundamental importance in drawing up new topographic maps.
For five years, from 1930 to 1935, Ruef flew a Messerschmidt Me-18 over China in the service of Gen. Chiang Kai-Shek. The general also sent Ruef on reconnaissance missions against the Communist insurgent Mao Tse-tung.
The Luftwaffe made him a major in 1935 and trained him as a military pilot; he was then put to work as an instructor.
By 1939 he had risen to become commander of the Reich's pilot training school in Hildesheim.
That was the beginning of modern German aerial reconnaissance. Ruef organized the training of the so-called photo officers to stress, as he himself put it, "the most scrupulous accuracy."
Unlike the Allies, with their area bombing techniques, the Luftwaffe preferred precision bombing. The tactic of using warplanes as "the extended arm of the artillery" led to the development of the legendary Stuka dive bomber -- and gave aerial reconnaissance an extraordinarily important role.