by J E Kaufmann
The JM cloches mounted a pair of machine guns that covered a limited sector across the fort's surface. These cloches had a small observation position on each side of the JM crenel. They were usually placed flush with the roof of the block and presented a smaller target than other types of cloches.
A special type of mortar cloche was designed for many of the blocks. It was flush with the surface and consisted of a special breech-loaded automatically fed 60-mm mortar. The purpose of this cloche was to shower the block's surface and surrounding area with bombs. These cloches, called cloches lance-grenade, were never ready for use because their weapon was not perfected. In addition to the GFM cloches for observation, CORF designed special observation cloches that mounted no weapons. One type had narrow observation slits and a small roof periscope. The other type was flush with the surface and mounted a huge periscope that rose above the ground. When not in use, the periscope was lowered and the cloche opening was sealed with an armored covering. Some ouvrages had special observation blocks exclusively endowed with these special cloches. In this case, the command post was usually situated below the observation block.
In each combat block the crew, whose number varied from twenty to forty men, slept in a special rest area situated at the lower level. These men were rotated back to the service area in shifts, but during the war many simply preferred to stay in their block rather than haul their gear back and forth. Each block had a filter room, rest area, storage for small arms ammunition, latrine facilities, and a stairway connecting it to the subterranean level of the fort. Some of the smaller blocks-those for observation only that had just a single cloche or weapons position-did not always have these features. However there were few of this type in the Maginot Line Proper. Most artillery blocks had a chamber for an M-3 magazine and elevators for hauling ammunition from the subterranean gallery to the combat level.
The underground gallery system was situated below most of the blocks, especially the artillery blocks, at a depth of twenty to thirty meters, depending on the terrain. The gallery system consisted of secondary access tunnels that connected the combat area to the main gallery, which was normally at a depth of about thirty meters. Additional facilities for the artillery blocks were located in the tunnels below, and included a machine room for operating the elevators, an M-2 magazine for maintaining a larger supply of ammunition for the guns above, and a room for expended shells. The access tunnels were usually sealed off from the main gallery by a set of armored air-pressure doors. In the majority of the ouvrages the main command post was located near the main gallery together with offices for the artillery, infantry, and engineer commands and a communications room. Telephone lines linked the command post to all parts of the ouvrage and order transmitters were found in the firing chambers of the gun rooms. In only a couple of ouvrages was the command post situated at a level between the subterranean works and the combat blocks.
A power sub-station, located near a point where the combat area of the fort began, received electrical power from. the service area. Its transformers and converters stepped down the power for redistribution to the combat blocks and other facilities. The power lines and the communications wires ran back to the service area along the main gallery. With few exceptions, the ouvrages had a rail system that connected the service area to the access tunnels through the main gallery. This was necessary since the length of the main gallery between the combat and service areas was up to 500 meters long, and the distance between the entrance block and the most distant combat blocks could easily exceed 1,000 meters. The train engine normally operated only in the main gallery, where it received its power from overhead cables and carried almost exclusively supplies and ammunition. The troops had to walk, or in the case of larger forts like Hackenberg, they were supplied with folding bicycles. At one or more points the main gallery was sealed off by armored doors designed to halt any enemy soldiers that might penetrate that far. In addition, at several points along the gallery there were special explosive-filled niches that would block the gallery when detonated. There were even internal blockhouses in a few of the forts.
All galleries had a slight incline so water could flow out of the fort through a drain located beneath the floor, which emptied at the side of a hill. Most drains were large enough for a man to crawl through and could serve as an emergency exit. A weapons position covered the length of the drain. The main gallery was usually wide enough or two sets of tracks near the EM, but the secondary tunnels only accommodated one set of tracks.
Most ouvrages were also provided with a secret emergency exit that was invisible from the surface because its upper chamber was filled with sand. When this sand was released into an empty room below, it allowed the men to enter the upper chamber and climb a ladder to the surface.
The main gallery began in the service area, near the entrance block. The gros ouvrages normally had two entrance blocks: one for the munitions called entree des munitions or EM, and one for the men, called entree des hommes, or EH. The EM was a large block that faced the rear and contained one or two firing chambers for antitank guns, JM and FM like the infantry blocks. The roof of this block usually had two GFM and a lance-grenade cloche. A diamond fosse protected the exposed face of the block in front of the weapons crenels and the entrance. A permanent concrete bridge spanned the narrow fosse and a heavy iron grating barred access to the entrance tunnel. The grating was covered by a firing position for an FM at the end of the tunnel, adjacent to a heavy armored door. In front of the armored door and weapons position was a sliding bridge over a deep pit, known as a tank trap. This arrangement was standard for EMs designed for train cars of a narrow-gauge military railroad and for trucks. Those entrances that were not designed for railroad use had a slightly different design. Trucks and rail cars could be off loaded behind the armored doors, where the small train cars of the ouvrage awaited. This unloading area was defended by one or two interior blockhouses located in front of a second armored door leading to the main gallery. Depending on the elevation, access to the main gallery was either direct, by an incline using a special engine to move the cars at an angle, or by elevator. The incline was considered to be the most desirable for the EM, while the elevator was preferred for the EH.
The EH was smaller than the EM and had an "L" shaped entrance, a narrower entrance corridor, and no tank trap. A removable metal bridge spanned the fosse and the armored door sealed the end of the "L" shaped entrance, out of the direct fire of the enemy. In a few ouvrages a single entrance was used both for supplies and men and was called entree mixte or mixed entrance. It resembled the EM rather than the EH, which was too small for the protected unloading and movement of supplies.
The service area housed the caserne, or barracks area, and associated facilities. The caserne was designed to accommodate about one third of the garrison. It included showers, latrines, a large filter room, a well, water storage, kitchen, storage rooms for food stocks and wine off the kitchen, an infirmary, and, more often than not, a small detention area. The larger ouvrages also had an operating room and a dentist's office. Since there was no mess hall, the troops had to eat in the corridors, on shelves attached to the walls. The officers, however, were allowed the luxury of their own mess area. Electric heaters kept the temperatures in the caserne at comfortable levels.
In addition, the service area normally contained the usine, or engine room. In the gros ouvrages it held four diesel engines, two of which were used to maintain operations and the remaining two were kept in reserve. These engines supplied the fort's electrical needs. The fumes from the usine were expelled into the fosse of an entrance block, through special escape vents. In rare cases, when the usine was too far from the entrances, a special chimney block had to be built. Associated with the usine were the fuel and water storage areas, the converters, the transformers, and a work room. In peacetime or prior to combat, power arrived from the National Grid by underground cables after leaving a special fortified military sub-station by aerial cables.
> Another important feature of the service area were the magazines. The M-1, or main magazine, was usually located near the EM. It had smaller annexes for fuses and other types of explosives. Most ouvrages had an M-1, except Schoenenbourg, one of the most prominent exceptions, which had a special M-1/M-2 magazine near its combat blocks. To protect the rest of the ouvrage from the effects of accidental explosions, special protective measures were taken. They included a sprinkler system and curved access galleries to deflect the force of the explosion. In addition, the main gallery could be quickly sealed by a special seven ton armored door that was designed to slam shut automatically in the event of an explosion.
Finally, the service area housed workshops and garages for the maintenance, repair, and storage of the underground train located in the main gallery.
The surface of the ouvrage was protected by wire and anti-tank obstacles. Normally, the service and combat areas were surrounded by separate sets of obstacles. However, in some cases the individual blocks were similarly protected. The antitank obstacles consisted of several rows of rails embedded at various heights which connected most of the ouvrages. In the few ouvrages with two separate sets of combat areas, each set was covered by these obstacles. In some cases an anti-tank ditch and/or wall ran between the two areas and covered their individual blocks as well.
Originally, plans for the ouvrages called for encircling moats, but these turned out to be too expensive, especially during a period of economic depression. As a result only a few small sections were actually built, as mentioned. There were no mine fields because the French had not developed anti-personnel mines, but some anti-tank mines and booby-traps (anti-personnel) were implanted. The petits ouvrages were similar to the gros ouvrages but they had fewer combat blocks, and the few that had artillery mounted no more than 81-mm mortars. A number of petits ouvrages had originally been planned as gros ouvrages but were not completed as such. In most cases, their mission was either altered or became more circumscribed.
The few petits ouvrages that had a separate entrance block either had a very small entrance for men, like Lembach, or a mixed entrance, like Immerhof. This entrance was smaller than the EM of a gros ouvrage, and looked more like the EH. In most petits ouvrages, there was no special entrance block, but two or more of their infantry casemates included a regular entrance. Most petits ouvrages consisted of one to six blocks. The monolithic ouvrages were rather large because they had no subterranean galleries. Consequently, all their service facilities and mortars, which fired through the fosse, were at the lower level. In some petits ouvrages, the underground facilities could not be placed thirty meters below the surface because of the terrain. The usines of the petits ouvrages held fewer engines, and all their facilities but the combat blocks were built on a smaller scale.
The following is a list of gros and petits ouvrages with their main armament:
OUVRAGES RF of Metz PO Chappy GO Fermont GO Latiremont PO Mauvais Bois PO Bois du Four GO Brehain POAumetz GO Rochonvillers GO Molvange PO Immerhof GO Soetrich PO Karre GO Kobenbusch POOberheid GO Galgenberg POSentzich GO Metrich GOBillig GO Hackenberg PO Coucou ARMAMENT ENTRANCES 1 Inf Cas, 1 MG-Tur - 2 1 Inf Cas, 1 75-Tur, 1-75 Cas, 1 81-Tur, 2 MG-Tur, 1 Obs 2 2 75-Cas, 1 81-Tur, 2 MG-Tur, 1 Obs 2 Inf Cas, 1 MG-Tur - 1 Inf Cas/MG-Tur - 2 75-Tur, 1 135-Tur, 1 81-Tur, 2 MG-Tur, 2 Obs 2 2 Inf Cas, 1 MG-Tur - 2 2 75-Tur, 1 75/135 Cas, 2 135-Tur, 2 MG-Tur, 1 MG Tur/Inf Cas, 1 Obs 2 3 75-Tur, 1 135-Tur, 1 81-Tur, 2 MG-Tur, 2 Obs 1 1 81-Tur/Inf Cas, 2 MG-Tur 2 2 75-Tur, 1 135-Tur, 2 MG-Tur, 1 81-Cas 1 Inf Cas/MG-Tur - 2 1 75-Tur, 1 75-Cas, 1 81-Tur, 2 MG-Tur, 1 Inf Cas, 1 Obs 1 Inf Cas/MG-Tur - 1 135-Tur, 181 -Tur, 1 MG-Tur,2 Inf. Cas, 1 Obs 2 1 Inf Cas/MG-Tur - 1 75-Tur, 1 75-Tur/Inf Cas, 1 75-Cas, 1 135-Tur, 2 1 81-Tur, 1 MG-Tur, 1 Inf Cas/MG-Tur, 1 Inf Cas, 2 Obs 1 1 75-Tur/75-Cas, 1 75-Cas, 1 81-Tur, 1 MG-Tur, 2 Inf Cas, 1 Obs 2 1 75-Tur, 2 75-Cas, 1 135-Tur, 1 135-Tur/135 Cas, 2 81-Tur, 1 MG Tur, 2 MG Tur/Inf Cas, 2 Obs, 5 Inf Blocks in AT obstacle 1 Inf Cas/MG-Tur, 1 Inf Cas - GO Mont des Welches GO Michelsberg PO Hobling PO Bousse GOAnzeling PO Behrenbach PO Bovemberg PO Denting PO Village de Coume PO Coume-Annexe Nord PO Coume PO Coume-Annexe Sud PO Mottemberg PO Kerfent PO Bambesch PO Einseling PO Laudrefang PO Teting RF of Lauter PO Haut Poirier POWelschoff PO Rohrbach GO Simserhof GOSchiesseck POOtterbiel GO Grand Hohekirkel PO Lembach GO Four a Chaux GO Hochwald GO Schoenenbourg 2 2 75-Tur/Inf Cas, 1 81-Tur, 1 MG-Tur, 1 Obs 1 1 75-Tur, 1 135-Tur, 1 81-Tur, 1 MG-Tur, 1 Inf Cas 1 MG-Tur, 1 Inf Cas, 2 Obs - 1 1 Inf Cas/MG-Tur, 1 Inf Cas, 1 Obs 2 2 75-Tur, 1 135-Tur/135-Cas, 1 81-Tur, 1 MG-Tur/Inf Cas, 1 MG-Tur 1 MA Tur/Inf Cas 1 MG-Tur/Inf Cas, 1 Inf Cas, 1 Obs - 1 MG-Tur, 1 Inf Cas, 3 Obs - 1 MG-Tur, 2 Inf Cas - 1 MG-Tur, 1 Inf Cas, 1 Obs - 1 MG-Tur/Inf Cas - 1 MG-Tur/Inf Cas, 1 Inf Cas - - 181 -Cas, 3 Obs 1 MG-Tur, 1 Inf Cas, 1 Obs - 1 MG-Tur, 2 Inf Cas, 1 Obs - - 1 MG-Tur, 2 Inf Cas 1 MG-Tur/Inf Cas - 1 81 -Cas, 1 MG-Tur, 2 Obs - 1 MG-Tur, 1 Irnf Cas - 1 1 AM-Tur, 2 Inf Cas - 1 AM-Tur, 2 Inf Cas 1 1 AM-Tur/Inf Cas, 1 MG-Tur/Inf Cas 2 1 75-Tur, 2 75-Cas, 1 135-Tur, 2 MG-Tur/1 35 Cas, 2 81-Tur/Inf Cas 2 1 75-Tur, 1 135-Tur, 1 81-Tur, 1 81-Cas, 1 MG-Tur, 1 Inf Cas, 3 Obs 1 1 81-Tur/Inf Cas, 1 MG-Tur, 1 Inf Cas, 1 Obs 2 1 75-Tur, 1 MG-Tur, 2 Inf Cas, 1 Obs 1 2 Inf Cas, 1 Obs 2 1 75-Tur, 1 135-Tur, 1-81 Tur, 1 MG-Tur, 1 Inf Cas, 10bs 2 75-Tur, 2 75-Cas, 1 135-Tur, 1 135-Tur/135-Cas, 3 181 Jur, 2 MG-Tur, 2 75-Cas in fosse, 9 blocks on AT ditch 2 2 75-Tur, 1 81-Tur, 1 MG-Tur, 2 Inf Cas
NOTES: GO=Gros Ouvrage, PO=Petit Ouvrage, Obs=Observation and/or GFM cloches, Cas=Casemate, Tur=Turret, / = combination, Inf=Infantry, MG=Machine Gun, 81=81-mm Mortar, 135=1 35-mm Howitzer, 75=75-mm Gun, AM=Mixed Arms. Only entrance blocks not serving as combat blocks are listed under Entrances. Some PO entrance blocks were very small.
Another type of structure in the Maginot line was the interval casemate found in the main line between ouvrages and designed by CORF. These casemates followed standard blueprints and were similar to some of the infantry casemates of ouvrages mounting anti-tank guns, JM and FM. The main difference was that the CORF casemate had its own small usine since it was an independent position. Some were double casemates, meaning they had firing positions on both flanks. Only the cloches were devised for observation and defensive firing to the front. Like the casemates of most petits ouvrages, the CORF casemates had an armored door entrance that faced to the rear and often a diamond fosse. Each casemate sheltered a garrison of about two dozen men and one officer. Communication was by telephone, via underground cable linked to adjacent positions and ouvrages.
The CORF observatories were smaller than the casemates and were manned by a few men with communications equipment. They were located at key points with a good view of the surrounding terrain. Their job was to keep the artillery ouvrages informed of the enemy's movements.
Abris, or troop shelters, were found to the rear of the other positions of the main line. They were like small casernes with facilities for a command post and came in two types: the cavern abri and the monolithic surface abri. The cavern abri generally had two small entrances, each defended by a small arms position that led to the subterranean facilities below.' The monolithic abri generally consisted of two levels and had two GFM cloches above. This type of abri was similar to the casemates of an ouvrage in that it was covered by a layer of earth, (except on its rearfacing facade), and was usually built into a reverse slope or a hill.
When the war began, new types of non-CORF positions appeared and still newer types were added when work began on the New Fronts. These included a mixed variety of non-CORF casemates and blockhouses. Many old FT-17 tank turrets and chassis set in concrete became observatories and small bunker-like positions. During the war, the army built many non-standard blockhouses throughout the line.
The Sarre Gap was defended not only by dams for flooding, but also by a number of small blockhouses. The Service Techniques du Genie (STG), or Technical Service of the Engineers, designed fortifications to cover areas not protected by CORF works and, after 1938, built some STG type casemates mainly in the Sarre Gap. These STG positions were smaller and usually held fewer weapons. A few were
designed to mount a cloche that was not installed in time for the campaign.
The support positions, which included permanent casernes, were generally located behind the main line of resistance. However, there were small temporary casemes near each ouvrage. Only the RF of Metz had fortified sub-stations for relaying power from the National Grid to the ouvrages. Supply, ordnance, engineer depots, and even some positions for heavy artillery were also located in the rear area. At Thionville the French rearmed the gun turrets of the three old German Feste of Illange, Koenigsmacker and Guentrange with 105-mm guns to support the main line.'
Although they were not a part of the Maginot Line Proper, the Rhine Defenses were built at the same time. They included no forts along the Rhine, except for old ones, and consisted mostly of casemates located along the river and behind the river line. These casemates consisted of a single level because the water table did not allow for underground construction. Each was a typical CORF casemate with its own facilities to operate independently with a platoon-sized force. Most had a GFM cloche. Over a hundred casemates occupied the river and village lines, but even those on the river provided only flanking fires. These river positions covered the key crossing points and had to be heavily camouflaged, yet they were not difficult to detect. The village line had the largest casemates. A large number of smaller blockhouses mostly occupied a position between the casemates of both lines. The blockhouses in the Rhine sectors were similar to the many non-standard types built by the army and only held a few men. Between the river and village lines a number of abris and blockhouses guarded key points, and roughly, formed a second line in the heavily wooded terrain. In a few sectors defensive positions near the Ill River created a fourth line.