Israeli warplanes have dropped thousands of pink and yellow propaganda leaflets into Lebanon over the past week. Anyone who offers aid to Hezbollah, one of the flyers says, "is putting his life in danger." How do you drop leaflets from an airplane?
With a leaflet bomb. Capt. James Monroe invented the American propaganda bomb during World War II. Thousands of pieces of paper were stuffed into a laminated paper cylinder with a detonator and a delay, and then loaded into a B-17. The "Monroe bomb" exploded on the way down, sprinkling leaflets over enemy territory from a low altitude. The Air Force quickly developed more advanced versions of the same idea. For many years, their standard leaflet bomb was the M129, a fiberglass case that holds up to 80,000 flyers.
The leaflet bomb reduces the effects of wind, which can easily blow leaflets away from their intended target. This problem was more acute during World War I, when many pilots made their leaflet drops by hand. The barnstorming pilot aces of the early 20th century also used hand-drops to distribute advertisements for their air shows. Charles Lindbergh had his mother toss notices from the cockpit of his plane.
All those loose papers flying around the cockpit could get dangerous, though. By the 1940s, pilots had devised a safer system. First, they filled cardboard boxes with flyers, then attached the lids of the boxes to the plane with a cable. The boxes would fall from the airplane in one piece until the cable went taut. The lid would then pop off, releasing the leaflets at a safe distance from the plane.
The cardboard-box method continues to be both cheap and effective. In the past few years the United States has used tethered boxes to distribute millions of propaganda flyers from low-flying planes over Iraq and Afghanistan. (In the run-up to the war with Saddam, the U.S. also bombarded Iraqis with e-mails and cell phone calls.) In general, propaganda-droppers use leaflet bombs when they need to fly at a safe, high altitude. If they can fly low, they use the cardboard-box technique.
Military research on leaflet dispersion has focused on how to improve the M129 bomb, which tends to burn up some flyers when it bursts. Psychological warfare units have also experimented with remote-controlled parachutes and pneumatic systems that use pressurized gas to propel leaflets out of a plane.
According to the PsyWar Society—which publishes a quarterly magazine called The Falling Leaf—aerial leaflet propaganda goes back at least as far as 1806, when a British admiral used kites to drop messages on the French. The French used balloons to drop leaflets on the Prussians in 1870, and the practice continued at least until the Second World War. Twentieth-century armies also fired leaflets at each other in howitzer shells, grenades, and rockets.
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Explainer thanks Herb Friedman of Psychological Operations Veterans Association.