American bombardiers said they could drop a bomb into a pickle barrel from 20,000 feet. The device they used to do it…

American bombardiers said they could drop a bomb into a pickle barrel from 20,000 feet. The device they used to do it cost America over a billion dollars to build. 90,000 of them were manufactured during the war. It was one of the most closely guarded secrets in the country. The Nazis had already stolen the plans in 1938. This is the story of the Norden bombsight..🧵1/5

🧵 2/5 By the late 1920s a Dutch born American engineer named Carl Norden was working on a problem no air force in the world had solved. How to drop a bomb from 20,000 feet in the air, travelling at hundreds of miles per hour, into something the size of a small building. The maths was punishing. The bomb had to be released early enough to fall through wind and air resistance to a target the bombardier could no longer see. Speed, altitude, drift, temperature, the curvature of the earth. All of it had to be calculated in real time by a man looking through a small telescope in a moving aircraft. Carl Norden built a machine that did it for him. The Norden bombsight was a 50 pound electromechanical analog computer containing roughly 2,000 precision parts. Gyroscopes. Motors. Gears. Mirrors. A telescopic sight. A rotating directional indicator. And an autopilot link that allowed the bombsight to fly the aircraft itself during the final minutes of the run, holding the bomber rock steady on its approach. The bombardier set the variables. The Norden calculated the release point. The Norden flew the aircraft. The Norden dropped the bombs. In controlled tests it seemed astonishingly accurate.

🧵 3/5 The United States government treated the Norden as one of the most closely guarded secrets of the war. Some historians have argued the secrecy was partly a decoy, meant to draw enemy intelligence away from the Manhattan Project. Whether by accident or design, the programme is commonly cited as having cost over a billion dollars, and 90,000 bombsights came off the production lines between 1939 and 1945. The security around them was extraordinary. The sights were carried to and from aircraft under armed guard in locked metal cases. They were installed before every mission and removed afterwards. On the bomb run, the bombardier was the only man permitted to operate it. Each installation included a thermite grenade. If an aircraft was going down or about to be captured, the bombardier was supposed to destroy the sight with it. The grenade burned at over 4,000 degrees, hot enough to reduce the whole machine to unrecognisable slag. This was the most carefully protected piece of military technology in America. It had also been completely compromised before the war began.

🧵 4/5 The Norden was manufactured in a factory on Lafayette Street in lower Manhattan. Many of its craftsmen were of German descent. Carl Norden himself spoke fluent German. One of his most trusted employees was a 36 year old assembly inspector named Hermann Lang, who had emigrated from Germany in 1927 and become a naturalised American citizen. He lived in a German American neighbourhood in Queens. What nobody in America knew was that Lang had been a Nazi stormtrooper, had been on the streets of Munich during the Beer Hall Putsch in 1923, and had belonged to the party from its earliest years. In 1937 he was recruited into a German espionage network in New York, the Duquesne Spy Ring, led by a South African born agent named Fritz Duquesne. Lang's job was simple. Memorise the Norden plans one section at a time, and reproduce them at home at his kitchen table. In 1938 he travelled back to Germany and met Abwehr Colonel Nikolaus Ritter in Hamburg. From memory, on the floor of Ritter's office, he reconstructed the plans of the Norden bombsight. German intelligence paid him for it.

🧵 5/5 The FBI got an anonymous tip in 1940 and watched the ring for over a year. In June 1941 they arrested 33 people, the largest espionage roundup in American history. Hermann Lang was convicted by a Brooklyn jury on 13 December 1941, six days after Pearl Harbor, and sentenced to 20 years. The Norden stayed classified through most of the war. Bombardiers kept carrying thermite grenades. The sights kept travelling under armed guard. Meanwhile hundreds of Norden equipped bombers were being shot down over Germany, and the Luftwaffe collected the wreckage of every one of them. By then the Germans had held copies of the design for five years anyway. And the accuracy never matched the promise. In combat, the average bomb dropped from a Norden equipped B-17 landed around 1,200 feet from its target. Only about 16 percent came down within 1,000 feet. But in August 1945 the Norden was still aboard the two B-29s that flew to Hiroshima and Nagasaki. Major Thomas Ferebee used one to aim the first atomic bomb at a bridge in central Hiroshima. He missed his aiming point by around 800 feet. It made no difference. Lang was released in 1950 and deported to Germany. Carl Norden died in 1965, aged 85. The most carefully protected secret weapon in America. The one the Nazis had already stolen. This was the story of the Norden bombsight. I post a story like this every single day. Most people never see them. Follow so you don't miss the next one.