By Pierre 'Piet' MICHIELS with particular thanks to Phil BALL for the translation.
After the Casablanca Conference in 1943, the Allies effort is focused on the progressive destruction of the German industrial system and the demoralization of the population through air raids on urban and semi-urban areas.
In response, the Luftwaffe strengthens Himmelbett. litterally a "canopy bed". In fact and in an imaging way, the german interception system is based on the four pilars that are a night fighter, a long range FREYA radar and two short range WURTZBURG radars. The integration of these elements is made to protect the german Reich.
So, besides the presence of air monitoring stations located near potential targets in the heart of the Reich, access to Germany is monitored by a belt of surveillance radars.
Each sector is under the operational control of an NJRF Nacht Jagd Raum Führer, itself under the supervision of a Nacht Jagd Gruppe.
The radar installations form a complete integrated system and are grouped into three-dimensional areas called Raum, numbered 1 to 9.
The control centre of each of these sectors governs every detection station spread across the LuftNachRichten Regiments geographical area.
Each Regiment is formed of at least three Companies. Usually each of these Companies is equipped with one of the medium-range detection Freya radar and a tandem of two short-range detection Wurtzburg-Riese radars operated in pairs.
The achievement of a three-dimensional night air interception is based on the complete integration of the ground component and the air component.
The radars detect targets, selects one, and then directs the interceptor towards this spot.
The direction and distance of the stream of bombers are first established by the Freya radar, at an average range of 130 km. Whilst very accurate in terms of lateral azimuth (01 °) and distance (250m), the Freya does not yet provide an accurate estimation of the flying altitude.
The interception is then entrusted to the tandem Wurtzburg-Riese radars which have a range of 50 km, with accurate lateral and vertical azimuths (01 °), allowing position identification in three dimensional space within 250m. or thereabouts.
When in range of the two Wurtzburg-Riese radars, a target is selected by the co-ordinator of the stellung, at Company level. Each radar is then assigned to a specific target. The beam emitted by the first radar Stellung rot tracks the bomber, the other beam emitted by the second radar Stellung blau follows the night fighter.
Operational in mid-1943, the system is known as Seeburg-Lichtenstein-Verfahren. At this stage of the war, in the stellung in the combat room, the device consists of a two dimensional projection of the respective positions of one single bomber and one single night fighter. Their location and their three dimension movements are collated at the radar station in the control room of the Company, on a Seeburg glass table.
Usually the night fighter is orbiting a beacon while waiting to be assigned a target. As its inboard radar Lichtenstein is short range, it is then guided to its target by the co-ordinator of the stellung. At a distance less than 3 km from its target, the bordfunker aboard the night fighter can guide its pilot within firing range.
As a response to this complex system of detection, the Allies decide to send a high number of bombers to a single Raum to saturate the interception capacity and limit losses to about 6 bombers per hour and per sector.
The data collected after each raid is used to calculate statistically the optimal spacing in altitude and distance to minimize losses and mid-air collisions while maximizing air penetration.
In response, the Luftwaffe then concentrates night fighters when the bombers are first detected and increases the number of Würtzburg-Riese radars by hundreds.
The Raum 7, which includes the Belgian region of sud-luxembourg, is attached to NJRF 7 of Florennes where I./NJG4 is based, the 1st squadron of the 4th night fighter group.
In the summer of 1943, this unit is primarily equipped with Messerschmitt Bf110 night fighters.
Under the supervision of 3. Jagd-Division, the coverage of the territory of sud-luxembourg is provided by the Luftnachrichten Ausbildungs - Regiment 301, whose headquarters are established in December 1942 in Saint-Hubert. This Regiment is composed of three Companies, two of which are positioned in Belgium and the third in France.
The two ground radar installations located in Belgium are one near La Roche, code-named Rochen, and the other one near Bouillon, code-named Bulle.
Another identical installation is located on the other side of the border near Damvillers, code-named Darche.
The site of Bouillon, Stellung 2 / Ordnung BULLE, is occupied by the 2nd Company of the 301st Regiment of night air research, which is composed of a little over 220 men, some of which are Malgré Nous (forced conscripts) from French Alsace-Lorraine. The Regiment will be disbanded in september 1944 after the evacuation of the site, preceded by its deliberate destruction by the Germans fleeing advancing American troops.
Located at a place called La Croix Blanche, the radar station is conventionally composed of a Freya radar lz FuMG 401 and two Wurtzburg-Riese radars FUSE 65, plus the usual buildings for operations, housing and technical maintenance.
As you come from the village of Mogimont, the first Wurtzburg-Riese radar concrete basement is visible on the left of the farm road, halfway between the Rue de la Charite and the farm of La Croix Blanche.
If you then turn left towards Dinant, you can see the second Wurtzburg-Riese radar concrete foundations 100m to the left of the road to Dinant.
Continuing in this direction, just after a small wood of tall pines, a sunken road overgrown by vegetation leads you right into the Freya radar site.
Opposite, are the ruins of a house and the foundations of a Heinrich-Pieler tower.
Placing the three radars on a north-south axis avoids them causing each other interference and allows a clear search to the east or west covering the in-bound or out-bound bombers.
In addition to the plinths and the characteristics of the foundations, the nature of the structures is recognized by Madame Denise GAUSSIN, who is 13 years at the time and lives at La Croix Blanche farm.
A short distance from the farm, the two structures being used for Wurtzburg Riese-FUSE 65 radars are constructed of concrete of a regulation pattern known as Regelbau V229. The side opening is protected by a door which provides access to the technicians responsible for the maintenance of the electric engine that provides the power to rotate the parabola.
These two structures are still visible today, each flanked by an underground shelter which was used as a rest room for the 4 operators on duty.
The height of the two structures is precisely the same so as to eliminate any error in the evaluation of the trigonometric position of the targets.
Designed in 1936 by engineers working for Telefunken with WT Runge, and the structure manufactured by the Zeppelin Company in Friedrichshafen, the Würzburg-Riese radar was first tested at the Luftwaffe’s centre in Rechlin.
Würzburg-Riese Fuse 65 radar is the most common version of German short range interception radar.
With a power of 8 kW, it emits wavelengths from 0.53 to 0.67m.
Its parabola measures 7.5m. in diameter, and its standard weight, including the cabin which houses the 4 operators, is 12 tonnes.
Placed on its concrete plinth, the radius of rotation is 360 °.
Approximately 1500 were made and the Würzburg-Riese is considered one of the best radars of WW2.
The Freya lz Fuse 401 radar is commonly installed on a four-legged metal structure. It therefore requires a simpler mounting and plinths are provided for each of its four feet.
Placed vertically on a hexagonal control room, the pole which supports the entire grid structure rotates 360 °.
The actual site is only partly backfilled and concrete elements are still visible.
Designed and manufactured by GEMA, the Freya radar provides an azimuth pointing at medium range.
With a capacity of 15 to 30 kW, it emits wavelengths of 2.10 to 2.60 m.
Its rectangular antenna is approximately 6m wide with a total height of about 13m.
Its standard weight in running order, with the cab, is 6 tons.
Madame Denise GAUSSIN of Mogimont still owns fragments of the wire mesh that covered the radar ladder structure.
In addition the barracks, with a typical architecture in the shape of an H, U, L, T or I, include buildings for operations, maintenance and housing.
The foundations of the buildings have been identified by Madame Denise GAUSSIN and are still visible near the farm of La Croix Blanche and located in between it and the radar site.
The site is now completely overgrown by vegetation.
Classically, the T-shaped building houses the central operations room including the Seeburg glass table, whose foundations is still visible today.
The shape of the building and layout of the interior walls are standard and the foundations are still visible. The layout is identical to descriptions obtained from captured German technicians working on other sites.
Weakly defended by small arms, the radar station of La Croix Blanche is devoid of any form of air defence and is not the object of air attack prior to September 1944.
Indeed, the high number of this type of installation makes it a low interest strategic objective for the RAF. Moreover, its latticed structures are insensitive to classic bomb blast and can be quickly replaced.
The detection of bombers by German radars is considered as inevitable by the Allies.
The USAF overcomes it by day with a dense defence network in the bomber stream. The RAF Bomber Command considered that darkness is the best ally of the crews who fly by night.
With such equipment in the summer of 1943, the 2nd Company of the 301st Regiment is able to ensure the interception of any bomber within its reach. It will have a determinant role in the destruction of DS690, the Lancaster bomber that crashed at La Cornette on the night of July, 13th to 14th, 1943.
(1) In Gyges.dk
(2) in lexikon-der-wehrmacht.de
(3) de Michael Holmes, répertoire de l’organigramme de défense aérienne dans lequel la dénomination est 6. Funkmess Ausbildungs Kompanie,
(4) in geschichtsspuren.de / Stellung 2. Ordnung BULLE
(5) in deutsches Atlantikwall-archiv / Funkmess (ordnungs) stellungen in Belgien
Picture's credit to : Gyges.dk, Gyges.dk, Gyges.dk, Wikipedia.org, Gyges.dk, Mr Pierre Michiels, Gyges.dk, Mr Pierre Michiels, Mr Pierre Michiels, Gyges.dk, Gyges.dk, Gyges.dk, Gyges.dk, Mr Pierre Michiels, Mr Pierre Michiels, Gyges.dk, Mr Pierre Michiels, Wikipedia.org