Decoys

Devices used to draw the attention of an enemy away from a more important target. Active decoys are the principal method of self-defense for military aircraft and intercontinental ballistic missiles (ICBMs). Passive decoys, or dummies, are used to deceive visual intelligence such as photo reconnaissance.

The main threats to modern military aircraft are anti-air missiles, which travel faster and maneuver better than the best jet fighters. Heat-seeking missiles are designed to follow heat sources such as the jet exhaust of a modern aircraft. To elude heat-seeking missiles, a jet may release decoys called flares, which are tubes containing magnesium, a highly flammable element that burns with an intense white heat. Because flares initially burn hotter than jet exhaust, they may confuse the missile by offering it several hot targets, giving the aircraft a chance to escape.

Radar-guided missiles use radar to locate their targets, so flares are useless against them. However, radar is vulnerable to a type of decoy known as chaff, tiny strips of aluminum foil that the aircraft releases in large bunches. These metallic clouds of chaff appear as separate targets to the missile's radar. As with flares, the idea is to confuse the missile long enough for the aircraft to escape.

Although ICBMs travel much faster than aircraft, they too are vulnerable to interception. An antiballistic missile (ABM) is designed to target an incoming ICBM and destroy it high in the atmosphere before the ICBM can deliver its warhead. To counter ABMs, most ICBMs carry multiple fake or dummy warheads as decoys. The dummy warheads separate from the ICBM at the same time as the real warhead. They are designed to jam the radar that the ABM uses to track the real warhead and to confuse the ABM by offering it several targets.

Active decoys work by fooling systems that sense unseen properties of an object, such as the heat it puts out or its ability to be detected on radar. By contrast, passive decoys work by fooling the eye. Most of the visual intelligence information gathered today comes from aerial photographs taken by spy satellites and reconnaissance aircraft. Aerial reconnaissance is an efficient way to gather large amounts of data, but one can fool the camera by creating dummy tanks, planes, guns, and trucks. Items that appear obviously phony up close can look real enough in an airborne photo to deceive even trained analysts.

Dummy troops and equipment played a key role in the Allied invasion of France in 1944. The Germans expected the Allies to invade at Calais, the closest point in France to the English coast. The Allies, however, decided to invade much farther west, in Normandy. To disguise their intentions, the Allies created a fake army in the area of England closest to Calais. The so-called First U.S. Army Group (FUSAG) consisted of thousands of cardboard dummy tanks and airplanes, fake troop barracks and supply dumps, and enough humans to give the appearance of great activity. Even after the actual invasion had begun, the Germans were convinced that FUSAG was still going to invade at Calais and they refused to send reinforcements to [Page 184]Normandy. By the time the Germans realized they had been deceived, the Allied forces were well established in France.

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