World War II Day by Day

London, England • February 27, 1942

Under the cover of darkness on this date in 1942, 119 British para­troopers kicked off Opera­tion Biting when they para­chuted into Nazi-occu­pied Nor­mandy close to a German radar sta­tion in the parish (commune) of La Poterie-Cap-d’An­tifer, 12 miles north of the large French har­bor of Le Havre. A num­ber of what were in­ferred to be ground radar instal­la­tions had been iden­ti­fied by the Royal Air Force during aerial recon­nais­sance in late 1941, but their exact pur­pose and, of course, the nature of the equipment housed inside were yet unknown.

On landing, the well-armed para­troopers quickly over­came the lone sen­try guarding the Wuerz­burg radar array, dis­assembled the 10‑ft dish an­ten­na as a near­by enemy pill­box fired on them, removed and packed vital com­po­nents, and left for the near­by beach at Brune­val. (The com­mando-type raid is some­times known as Opera­tion Brune­val.) From the beach six Royal Navy landing craft took the raiders and their lib­er­ated booty, including one German radar tech­nician, back to England where the tech­no­logy could be studied and counter­measures designed and im­ple­mented to neu­tral­ize its effec­tive­ness. That was when British scien­tists dis­covered that all German ground-based radar sta­tions oper­ated on a small num­ber of fre­quen­cies, and that the radar sta­tions could be easily jammed by air-dropping alu­mi­num strips (vari­ously called “window” or “snow­flake”) to flutter down like a cloud, thereby swamping an operator’s radar screen with multiple returns (“blips”).

Initially British Prime Minister Winston Churchill forbade RAF Bomber Command from dropping reflecting chaff over German targets—thinking the Luft­waffe might get wise and apply the same strategy over British targets. That would of course con­fuse British radar opera­tors (and anti­air­craft bat­teries), leading to untoward con­se­quences on the ground. He relented after several months. Oper­a­tion Gomor­rah, the huge and devas­tating Allied bombing raids on the North German port of Ham­burg in late July/­early August 1943, suc­ceeded in part by air-dropping this reflecting chaff. For hours before the D-Day landings on June 6, 1944, British planes dropped tons of tin­foil strips over the German-held French coast of Normandy to con­fuse enemy radar oper­a­tors while 7,000 Allied ships approached the invasion zones undetected. Even though Germans had pio­neered its use—reflecting chaff was known as “Duep­pel” in German—they did nothing to prepare themselves for its use by their foes.

The month before Oper­a­tion Gomorrah, after a British photo inter­preter had iden­ti­fied a stack of Wuerz­burg dish anten­nas in a manu­fac­turing yard in Fried­richs­hafen on Lake Con­stance (Southern Germany), Churchill ordered the RAF to bomb the site. Not­with­standing suc­cess­ful Allied counter­measures like tossing tin­foil clusters from air­planes during bombing raids and the 1943 aerial assault on the sus­pected radar pro­duc­tion facility on Lake Con­stance, some 4,000 Wuerz­burg stations found their way into Wehrmacht service starting in 1941.
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German Ground-Based Wuerzburg Radar Equipment

Left: RAF photo-reconnaissance picture of the Wuerzburg radar array (dark round object left in photo) adjacent to a large Victo­rian ginger­bread villa, which French under­ground agents later con­firmed con­tained a machine-gun emplace­ment, not far from the Norman village of Brune­val, early December 1941.

Right: A Wuerzburg radar apparatus (Funkmessgeraet in German) installed on the English Channel coast, occupied France, 1943. For a cost of two dead, two wounded, and six missing, the daring and success­ful Febru­ary 1942 Brune­val raid provided Brit­ish in­tel­ligence with a close-up view of the new German air defense radars: their vital com­ponents, their impres­sive modular design that made main­te­nance and trouble­shooting easy even by oper­a­tional staff who were igno­rant of radar tech­no­logy, how the radar equip­ment was used, on what fre­quen­cies the radar operated, and what counter­measures could be used to thwart German radar sets, all of which were cru­cial if Allied long-range bombers and fighter air­craft were to operate effectively over Nazi-occupied Europe.

Left: An RAF Avro Lancaster dropping metallic chaff (the crescent-shaped white cloud in the left of the picture) to inter­fere with anti­air­craft bat­teries during a thousand-bomber stream over Essen, Germany. No date. One bene­fit of the Brune­val raid was that the Allies were able to test out metallic chaff (window) sizes and jamming tactics on a genuine Wuerzburg radar array itself.

Right: The effect of chaff on the display of a Giant Wuerz­burg radar scope. The effect of jamming appears in the left “jagged” half of the cir­cu­lar ring, con­trasting with the normal “smooth” (un­jammed) display on the right half of the circle, with a real target at the 3 o’clock posi­tion. On the jammed left side, the real target “blip” (an Allied air­craft) would have been indistinguishable from the chaff.

Military Radar: A Fascinating History