Thetis was the name of a floating

radar Radar is a detection system that uses radio waves to determine the distance (''ranging''), angle, and radial velocity of objects relative to the site. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, w ...

decoy used by German

U-boat U-boats were naval submarines operated by Germany, particularly in the First and Second World Wars. Although at times they were efficient fleet weapons against enemy naval warships, they were most effectively used in an economic warfare role ...

s during the

Second World War World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposin ...

. The device was stored dismantled in the bow compartment as a pole about two metres long. Assembly usually took place in the U-boat's conning tower, and could be assembled in about four minutes (''FuMT 2 - Thetis IIC''). Later versions could be launched from a standard torpedo tube (''FuMT 4 - Thetis US''). When deployed, it was extended to a total length of eight metres, half of which was submerged. The upper half had a series of reflectors that were tuned to

Allied An alliance is a relationship among people, groups, or states that have joined together for mutual benefit or to achieve some common purpose, whether or not explicit agreement has been worked out among them. Members of an alliance are called ...

anti-submarine radar wavelengths to give the same return signal as a U-boat. The number of Thetis decoys carried varied between different U-boats: * carried approximately 12 units during her 10th and last patrol between 16 January 1944 and 6 May; all were used in the

Bay of Biscay The Bay of Biscay (), known in Spain as the Gulf of Biscay ( es, Golfo de Vizcaya, eu, Bizkaiko Golkoa), and in France and some border regions as the Gulf of Gascony (french: Golfe de Gascogne, oc, Golf de Gasconha, br, Pleg-mor Gwaskogn), ...

. * carried 16 units during her 6th and last patrol between 25 January 1944 and 25 February. * carried an unknown number of units during her 21st and last patrol between 23 April 1944 and 4 May. * carried 15 units during her 13th and last patrol between 29 February 1944 and 13 March. U-575 would surface every night and laid a total of 10 on her outward voyage, the remaining units were to have been laid in the same area on her return. * carried 20 units during her 2nd and last patrol between 24 February 1944 and 6 March. U-744 used them on her outward voyage between 11°W and 12°W in the

. The first time the Allies knew about the "Thetis" was in a coded radio message to all U-boats transmitted on 11 January 1944. "Thetis" was introduced in January, when large numbers were released into the Bay of Biscay in July to simulate U-boat patrols during the

Battle of Normandy Operation Overlord was the codename for the Battle of Normandy, the Allied operation that launched the successful invasion of German-occupied Western Europe during World War II. The operation was launched on 6 June 1944 (D-Day) with the Norma ...

References

*{{cite web , title = HyperWar: Battle of the Atlantic IV: Tech. Intel. from Allied Comm. Intel. hapter 2 , url = http://www.ibiblio.org/hyperwar/ETO/Ultra/SRH-025/SRH025-2.html , accessdate = 2017-04-13 Weapons countermeasures

See also

References