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The Pédrefin V-2 radioguidance base was a  radioguidance base for V-2 rockets built by Nazi Germany near the village of Prédefin, located 16 kilometers northwest of Saint-Pol-sur-Ternoise in Pas-de-Calais, France. Constructed by the Organisation Todt during World War II. Its purpose was to track and guide V2 rockets launched from nearby the Watten and Helfaut-Wizernes bunkers using a radio guidance system called "Leitstrahl". Construction began in 1943, involving over 1,200 workers. However, advancements in rocket technology led to the abandonment of fixed radioguidance stations in favor of an inertial platform and mobile stations by early 1944. Consequently, the completed Prédefin site was transferred from the German Army to the Luftwaffe.

History
During World War II, the Peenemünde scientists, under the leadership of Werner von Braun, developed a radio guidance system for the V2 rockets. This system, known as "Leitstrahl," used beams of waves to guide the rockets to their targets with high precision. However, there was concern that the British could potentially jam the guidance system and divert the rockets off course. To counter this risk, the Organisation Todt was instructed to construct radar bunkers like the bunker of Roquetoire and a radio guidance base in the Pas-de-Calais region of France.

The purpose of the base was to track and guide V2 rockets launched from the KNW firing bunker at Eperlecques and the SNW firing bunker at Helfaut-Wizernes. These bunkers were located 38 and 24 kilometers away from the proposed site of the radio guidance base, respectively. The chosen location for the base was near the village of Prédefin, located 16 kilometers northwest of Saint-Pol in Pas-de-Calais.

The construction of the base was conducted in great secrecy, as it was part of Germany's offensive plan to launch the V1 and V2 weapons, known as "Wunderwaffen," by the end of 1943. The base was designed to ensure the rockets hit their intended targets with minimal dispersion. The radar bunker and radio guidance system were built to provide precise tracking and guidance capabilities for the V2 rockets.

This base played a pivotal role in the German military strategy, allowing them to maximize the effectiveness of their rocket attacks. The radar bunker provided crucial information on the trajectory and flight path of the rockets, while the radio guidance system ensured their accuracy. The base operated in coordination with the KNW and SNW firing bunkers, enabling the Germans to launch V2 rockets from these locations and guide them to their targets using the radio beams.

In summary, the radio guidance base at Prédefin in Pas-de-Calais was a top-secret facility constructed by the Organisation Todt during World War II. Its purpose was to track and guide V2 rockets launched from nearby bunkers using a radio guidance system called "Leitstrahl."

To be incorporated
THE RADIOGUIDANCE BASE V2 OF PRÉDEFIN (Pas-de-Calais)

Initially, the scientists of Peenemünde, under the leadership of Werner von Braun, had planned to radio-guide the V2 rockets to their targets using a system of beams formed by waves ("Leitstrahl"). This solution guaranteed very high precision and the assurance of hitting the intended target almost every time, without dispersion. However, it also posed the risk that the British might discover a countermeasure and a way to jam the guidance system, thus deceiving and diverting the V2 rockets.

In anticipation of the future launch of the miracle weapons V1 and V2 (Wunderwaffen), originally planned for the end of 1943, the Organization Todt (O.T.) received orders to build, in utmost secrecy, a radar bunker and a radioguidance base in the Pas-de-Calais department. This base was initially intended to track and radio-guide the V2 rockets launched from the "KNW" firing bunkers in Eperlecques (code-named Mannschaftsbunker) and the "SNW" in Helfaut-Wizernes (code-named Bauvorhaben 21, corresponding to the current La Coupole museum site), located 38 and 24 km away from the designated site, respectively.

The Germans chose a location 16 km northwest of the town of Saint-Pol, just west of the village of Prédefin (Pas-de-Calais), near the road connecting this locality to Heuchin. The base consisted of two groups of distinct installations arranged on the same axis, indicating their interdependence: the radar station and the radioguidance center.

Construction began at the beginning of 1943, and the building of this gigantic complex required 50,000 bags of cement (2,500 tons) transported to the site by a small auxiliary railway connected to the Saint-Pol – Hesdin railway. Over 1,200 workers and technicians contributed to the realization of various installations, including many Belgian and Polish workers assigned to masonry work, as well as some French from the S.T.O. (Compulsory Labor Service, established by Vichy at the request of the occupant). The workers were housed in barracks in a camp set up in the village of Prédefin and led by Commander Kramer, while the leaders of the Organization Todt stayed in a barracks built 200 m from the construction site.

Meanwhile, technicians at the Peenemünde research center managed to develop an inertial platform on board the V2 rocket, consisting of a set of gyroscopes and accelerometers. This allowed, in the early months of 1944, a complete abandonment of the initially planned radioguidance, albeit at the cost of greater dispersion of impacts and lower precision. The Prédefin site, whose construction was completed, was therefore transferred from the Heer (army) to the Luftwaffe, which transformed it into a radiolocation base included in the air defense system of the Nord-Pas-de-Calais region (air defense of Festung Europa).

The Mammut Friedrich Radar Bunker

Located 500 m from the radioguidance/radiolocation base, the bunker was topped by a gigantic Mammut FuMo 51 Friedrich radar.

This reinforced concrete bunker, built practically at ground level, measured 23 meters in length by 12.50 meters in width and 5.40 meters in height. It had a cover slab 2.00 meters thick supporting 4 concrete bases measuring two meters by five, in which were anchored the enormous 30-meter high metal pylons supporting the gigantic rectangular frame of the Mammut Friedrich radar, with a wingspan of 29 meters. Between the pylons, two concrete bases measuring 1.20 x 1.20 meters each, 3 meters in height, rose internally, containing a bundle of 12 tubes slightly protruding from the masonry for antenna connections.

In the middle of its southwest facade, the bunker had a main entrance with, on the left, two secondary staircases leading inside. On the right, the staircase led to the observation post above the southern corner. The bunker's entrance was flanked by a firing embrasure that opened into a small interior casemate, at the west corner of the building.

Inside, there was a command post equipped with electronic panels, two radar control rooms, an operations room equipped with 2 "SEEBURG" tables, and a machine room housing a 500 kVA generator, a boiler room, and a ventilation system leading to an opening in the cover slab.

Two and a half meters from the bunker were 2 annex buildings measuring 30 x 6 meters, which were completely destroyed by numerous Allied bombings. They included transmission rooms, barracks, and a guard post. At 50 meters away was a semi-buried concrete water tank containing the cooling water for the generator, as well as a 500 kVA transformer connected to the bunker and annex buildings by open concrete trenches.

The Radiolocation Base

400 meters from the radar bunker, to the left of the Prédefin – Heuchin road and along the railway line connecting Saint-Paul to Hesdin, an immense camp covering 25,000 square meters was built at a location called "Bois Lewingle." Its entrance was defended by a barrier and a concrete police post, next to which stood a 3-story building housing the guard's quarters, an armory, and the accommodations for the detachment ensuring the perimeter's security.

This camp, originally intended to house the tracking and radio-guidance installations for the V2, was transformed into an aerial radiolocation center by the Luftwaffe. It included 2 WÜRZBURG radars and a FREYA radar in emplacements, radio transmission antennas, a listening and transmission center, two transmitters, and a boiler room. The infrastructure was complemented by shelters, an observation post, a dozen buildings serving as quarters, a hospital, and a gas chamber for the training of non-commissioned officers. The largest building measured 100 meters in length and 20 meters in width and featured a wide central corridor around which numerous rooms were organized, including a kitchen, a cinema, and a ballroom. The station housed part of the headquarters responsible for the deployment of V1, various specialists and technicians, 80 soldier-telephonists, and 600 German military women ("gray mice") employed in communications. The site was evacuated by the German army in September 1944, facing the rapid advance of the Allied forces from the Seine, simultaneously with the other V1 and V2 installations in northern France.

A dummy replica of this complex was built 2 km away, in Fontaine-les-Boulans, to deceive the Allies. Since there were spies in the camp, the replica was bombed by the British with wooden bombs, demonstrating a distinctly British sense of humor.

The radioguidance/radiolocation base and the radar bunker were subjected to a total of about fifteen air bombings aimed at their destruction. The first bombings occurred on January 6 and 9, 1944, and the last raid took place on July 6 of the same year at 10:30 a.m.

This entire complex is partially intact and still visible today, except for the dummy base. However, the installations are difficult to spot in the landscape due to the growth of vegetation that has invaded the area.