A few technical notes about eastern Vallo Alpino
A destruction attempt suffered by this underground room has caused the vaulted ceiling to collapse. This reveals the thickness of the concrete vault (top center): about 40 cm.
|A very general description of a single, small center of resistance
The defensive work was called "center of resistance" (centro di resistenza) up to 1939 when the term was substitued by "firing center" (centro di fuoco) which began to appear on circulars and documents issued by the Ministry of War in Rome.
The obvious aim was to cover a strategic place by placing a weapon. This weapon, to be effective and create a serious problem to the advancing enemy, had to be protected as much as possible.
A bunker (pillbox) is then necessary to hide the weapon and to protect its crew. Additional measures were to be taken to support the men on the weapons so as to make them stand as long as possible the siege of the the enemy. So the adopted phylosophy was the underground system supporting the positions on the surface. The underground structure was obtained by digging into the limestone rock: that was the place for men to rest, to store food, water, ammunitions and spare weapons. The underground rooms were also where some further important devices were mounted.
Apart from the weapon positions, the whole body of a defensive work then lies underground and where its depth was considered it would be not sufficient, (to stand the largest artillery shots), the whole structure too was built in massive concrete; it was hidden beside any mountain slope and so much buried in the terrain to look as it were wholly dug into the sheer rock.
Infact, defensive works are classified as "opere in caverna" and "opere miste" i.e. totally underground works and works made up both by massive concrete and an underground part. Most of works on Eastern Vallo are mixed works.
The three main elements of these fortifications were: the positions (and bunkers hosting them), the local logistical underground system and the galleries connecting weapons positions with the dwelling quarters.
Tunnels walls were never left unfinished infact the inside rough rocky walls, ceiling and floor were completely lined by concrete and well-finished. Infact, apart from surface structures, cement was largely used in the underground system too: every rough rocky wall of the underground compartments was reinforced and lined by strong concrete walls (from a minimum thickness of as many as 30 cm on). These reinforcing concrete walls were even thicker in galleries and compartments near the surface.
While the ceilings of the innermost galleries dug in the rock were given a typical full curvature or upsidedown U shape (the deepest rooms also have vaulted ceilings), all the most external stretches of galleries, the most superficial compartments and passages like accesses and emergency exits have almost always flat ceilings enhanced by iron beams. As already said, the main reason why engineers chose to built concrete works instead of mix works (i.e works wholly made from massive concrete instead of a deep underground structure), was clearly due to the terrain. Being more superficial, concrete works or sligltly underground works required that the ceiling of every compartment would be reinforced by iron beams. In this case, additional walls were to be built: these more internal walls would stand the iron beams.
Being the general rule that of taking advantage of the terrain, every access is from the hind slope of the hill or from the inward side of a mountain pass. Every access or exit corridor has the typical "square S" plan or bayonet passage to protect the defensive work from shells, rock splinters or direct shots. Moreover, in most cases, an inside embrasure for an automatic weapon or light machine gun, is set at the S narrowing to protect either the entrance or a connection branch.
Many more details are given elsewhere in following chapters of this document.
Each bunker with regard to its access from the underground, is made so as to seal the rest of the defensive work off the wave caused by its eventual explosion.
A group of two or more weapon positions (rarely just a single position) and their local underground system constitute the smallest center of resistance.Some more details about the structure of medium and large size defensive works
Understanding this paragraph will require reading the Vth chapter of technical notes, where readers are given more strict definitions. As for the classification of defensive works, this paragraph focuses on a different point of view: what is described here is correct, but not as complete as the classification of chapter V. Infact, being simply no distinction between simple centers and aggregate strongholds (because they are functionally the same), medium size centers and medium size aggregate strongholds are uniquely referred to as medium size works. The same is valid for large size works. Inside both medium and large works groups, another distinction is mentioned here: that between only linear centers strongholds and aggregations of mixed plan centers. To evoid confusion, refer to the ultimate classification of Vallo works inChapter V.
I've been asked by someone whether there were an independent and self sufficient base unit (i.e. the smallest self sufficient center of resistance) by which largest defensive works were made up and if these units were all similar. Putting the question is other terms, one could guess if the hierarchical organization of the weapons had a well distinguishable corresponding organization of the structure so that the overall structure had actually made up by self-sufficient, independent and similar base units.
As for the similarity of these base units, the answer is: yes. Provided that the constituting smaller centers are actually observable, not only are they similar but they are arranged so as to give the whole center a sort of simmetry. In other cases the similarity is kept but the disposition and the size can be different since each smaller center may have a different number of positions and consequently logistical structure of different size.
As for the existance of a base unit, it must be said that it's well worth while observing the structure of bigger defensive works going into a bit more detail.
Medium size works
Regardless of the existance of a base unit, being the smallest defensive center a self sufficient defensive work, it is itself one base unit (a couple of weapons plus a local logistical system with ventilation and electrical power generation ); they are spread everywhere in type A, B and C defensive systems. So, if a base unit existed, larger works should consequently be formed by them the same way a wall is made up by bricks.
We could distinguish two types of medium or large defensive centers.
The first type of medium size work is the following: two or three centers were connected by underground galleries to constitute the whole center of resistance. These two or three smaller resistance centers are linked by galleries which are generally longer than local galleries linking the positions with the underground system inside the local center. It is impossible, of course, to give a general range of dimensions given the amazing variety of situations, but just to give a reasonable idea, i would say that local galleries can be as long as 10-15 metres, while galleries connecting separate centers can be 80-120-180 metres long.
The local centers of a medium size center of resistance were almost completely independent from each others. Infact, having its autonomous supporting underground structure along with a local ventilation system, each of them could get a certain degree of self sufficiency and independance from the rest of the medium size work. In this case, the medium size work of the first type may then be considered as made up by a series of smaller units (which were in turn small resistance centers) completely self sufficient so as not to compromise the overall firing capacity in case one center had completely been put out of order.
Anyway, these separate centers hadn't often the total independance from the others since many a center (generally two) had to share at least the same electrical power generator (maybe the ventilation system was considered essential, while defenders relied much on the capacity of the accumulators used to power the pumps).
A typical situation in which a medium size work was made up by smaller independent resistance centers is the protection of a road crossing an alpine pass: one center is placed on one side of the road and a second center is placed at the other side of the road. A gallery beneath the road links the two centers.
The second type of medium size work is the following: the whole structure is not made up by far and well distinguishable centers, thereafter it is impossible to observe any distinct base units making up the whole work. The structure may be complex and extremely variable. Infact, if we consider by definition the base unit having an independent ventilation system, we can easily detect all the ventilation pumps of a medium size work, but it's hard (and somehow useless) attributing that or this position to that or this possible center. The problem doesn't of course sussist if the constituting centers are well separated (first type structure).
Medium size fortifications can be seen on type A or B defensive systems.
Large size defensive works
The same distinction can be observed in largest defensive works. First type: works whose structure is constituted by many properly organized independent base units which are in turn gathered to make up either well separated centers of resistance or the whole work.
Second type: large works whose combat blocks and logistical systems are organized in so complex a structure that it is impossible to observe any self sufficient base unit.
It can sometimes be observed that a defensive work of the first type may be actually formed by two or more large defensive sub-works connected by long galleries. Each of these large sub-works is in turn formed by as many as two or more smaller sectors each of them is actually constitued, as seen above, by some independent base units. The overall result is that a certain number of the largest works is made up by many smaller centers having an autonomous logistical part serving one or more positions. In these cases each unit may be considered as a branch of the whole opera
The second type is somehow more common; infact most of largest works have not so well organized a structure. The adopted solutions can be so varied that both types seems to coexist: for instance, a large center is subdivided in two well distinguishable centers, but each of them has in turn no base units.
It seems obvious that the whole bunch of weapons of a large work was hierarchically divided in groups due to reasons attributable to the military organization: the work commander was over the two or three commanders of the two or three large sub sectors constituting the overall work and each of these sub-commander had in turn the responsability over the smaller sub subsectors (a battery for instance) by which their sub sector was made up and so on up to the commander of a couple of positions. The question is whether these subsectors can be in turn considered actual smaller resistance centers having a certain degree of self sufficency (first type) or they cannot be considered as stand alone centers (second type). As mentioned before, the answer is uncertain for a few largest centers and it is no for most of them. Infact, a large work could be made up just by a large group of positions without any intermediate structure or clearly separated subsectors having each an easily attributable logistical part. In some cases, the structure of a large work is so complex that it is difficult to attribute any positions or observatory to any smaller sub-sectors being themselves in turn difficult to point out.
Even if it were always possible to detect a constituting base unit, the question would be about how independent from the others each unit would be and which would be the minimum set of elements necessarily present in each of them. I would answer saying that each base unit has to have an independent logistical part with at least a ventilation system and an observatory (i recall that im looking for elements usefull to find a physical structure corresponding to the hierarchical division of the work and an observation post means a commander of the unit).
Sometimes, besides the shared power generator, two distinct centers had to share the same security exit and this prevented them to be two completely independent units (rare indeed situation).
To sum up what can be actually seen in the field: a part of medium size works are well structured and made up by separate smaller units. In most of larger works it is impossible to distinguish any independent base unit.
Enough of the thesis about the independent base units.
A bit of confusion rises when a medium size center of the first type was not called and considered as such if the constituting smaller centers were far from each other: in this case the two centers linking gallery was very long and the whole defensive work was indeed considered being two separate centers (unless the document referring to that defensive work goes back to a time prior to the construction of the linking tunnel). In my opinion, when two or more centers are linked by a tunnel, the overall structure becomes that of a single defensive work. Although made up, in this case, by two well separated and far independent centers, the overall system had only one electrical power generator .
What can be in addition said as an observation fact is that the smallest defensive works are constituted by a single center of resistance with one ventilation system and one electrical power generator. Many medium size works have two or more autonomous ventilation systems and generally only one electrical power generator. Largest works have many, more or less independent, logistical structures having anyway each of them its own ventilation system; the overall work has a certain numer of electrical power generators which generally are not so many as ventilators.
This last sentence could be explained saying that being ventilation pumps all the same (to be verified!), the number of served positions and compartments are similar; while, being electrical power engines able to be coupled, the served area can be bigger.
Weapons of eastern Vallo are machine-guns and anti-tank guns. Apart from mortars, flames throwers and ligher automatic weapons, since the defensive works of eastern Vallo have been actually made to host heavy and light machine-guns and small anti-tank guns, when i speak about the weapons i'm referring only to machine-guns and anti-tank guns. According to what can still nowadays be read on internal walls of corridors, italian soldiers were used to call any machine-gun by the term: "arma" (generic word meaning weapon); while they were used to refer to a cannon by the term: "pezzo".
The ideal situation would have been a weapon based at a position which was structured so as to completely protect shooters, servants, the weapon itself and to hide as much as possible the embrasure to avoid an easy detecting of the fire direction. The described ideal situation is a position set in a cave.
Speaking about fixed positions, there are three cases: the weapon is based outdoors, the weapon is underground based and the weapon is in a casemate.
As for outdoor positions, there were cases of temporary fields of which little or nothing more than any trenches, some barber wires poles or small concrete structures can now be seen. These areas could have been very extensive and it doesnt seem unlike that they were set up either to cover larger areas without any protection given by physical elements (areas of a certain defensive system requiring a type A defensive system), or to temporarly protect an area on which one or more defensive works were about to be born. In this case, a stony house to host stuff and men would take the place of tents and temporary lodgements. The outdoor weapon emplacements would have left the place to more or less big casemates or combat blocks (see forword in this document) and underground rooms to serve them would have been dug under and near the weapon positions. Once the weapon positions with their respective logistical underground systems had been finished, galleries would have been dug so as to link a certain number of positions to constitute one or more larger defensive works. This logical sequence (barracks, combat blocks, nearby underground compartments serving the positions and finally longer galleries connecting the sparse positions) privileges the urgence to always have the area protected by fire during all the construction phases. Since much depended on the terrain and the urgence to complete the protection of that area, the described sequence is not the general rule but it is much likely it had been so since it is supported by what now remains. So, when an area was lacking a suitable physical protection and a single defensive work was not enough (a wide hilly area, a plateau or a penetrable tableland which would have required a type A defensive system), it was first fortified by a temporarly stronghold of outdoor weapons. Dozen of machine-guns may have been scattered. It might be said that these particular areas were used as summertime strongholds or observation posts only, but more likely the truth is that these places were seldom manned in winter because excavations and the construction of concrete walls required the good season.
The different phases at which the overall construction was interrupted get confirmation by what still now remains. Not only are still visible the poor remains of the temporary stronghold with just one or more finished houses in the area, but, in case the interruption occurred at a following stage, there are the houses with a conspicuous number of small full operative defensive works spread on the area and not yet linked by galleries. In this last case, after the building of one or more houses, the construction went on following the described sequence.
Had the history assumed a different course (i.e. had Italy been given the time to complete her wall), many of those spread small defensive works would have been linked by galleries to make up one or more works as large and strong as a type A defensive system would have required.
To complete the chapter about outdoor positions, here it is a last note
about minor remains. In mountainous areas and behind the lines, simple trenches were
built at some road crossings as additional protection measures. A conventional short
trench was built at the road level. The trench has enhancing concrete frontal and rear
walls and it could host a half dozen men with one or two machine guns. Of course, are all
these minor defensive structures not considered as real defensive works.
As mentioned above, being obviously the main aim that to hide and protect as much as possible the weapon from attackers shots, the ideal situation was the completely underground position. The weapon position is hosted in a room obtained by an horizontal hole dug in the rock. The firing chamber is then completely sorrounded by rock: ceiling and all around walls are solid rock.
Useless to say that these were not only the most feared but the strongest positions: they could stand the largest shells shots. Infact, if the weapon is set underground, little more than the embrasure is visible from the outside.
The walls and ceiling of the hole were never left as rough surfaces, but were completely well finished and lined by enhancing concrete walls. In some cases, where the thickness and solidity of the frontal rocky wall were considered insufficient, the frontal wall of the underground position may have been made up or reinforced by a concrete wall as well. A steel plate could also be used. In spite of being underground, the ceiling of the firing chamber could have in addition been reinforced by steel beams.In the case a defensive work is completely dug in the solid rock, what can be seen from the direction the enemy is expected from, is only a rocky wall with a small weapon embrasure. Uneven terrains with more or less vertical rocky walls are the typical high mountain places exploited to make underground fortifications and all is required to make their weapons be effective.
Whenever it was impossible to set a weapon into a rocky cave, the concrete was used to build a bomb proof box completely surrounding the weapon position so as to protect it as it were set into a cave. In this case, massive concrete walls were thereafter used to substitue the solid rocky walls of an underground position. Casemates are the standard for lower mountains and hilly areas.
Since the ideal solution was thought to be setting a weapon completely underground to hide it as much as possible, these extremely solid concrete boxes were half buried and often built against any mountain slopes. To get as close as possible to the ideal situation, any casemate should have been hidden on the terrain by adapting its shape to the land so as to protrude as little as possible from the surface.
Anyway, where the structure was not close enough to the ideal situation, and this is clearly the most common case, the casemate is much more visible on the terrain. In any case, hower well hidden, many measures had to be adopted to camouflage as much as possible the casemate nake concrete surfaces.
The inner room in which there is the weapon position is called firing or shooting chamber: this room has the proper arrangements to host the weapon (weapon basement) and to protect shooters and servants (armors). The firing chamber, along with the weapon position, has a few small niches used as either small ammunition deposits or recesses for machine-gun cartridges cases.
As said, the frontal wall of the firing chamber may be in addition equipped by a steel armor whose details will be given in chapter III. Although not always present, the armor protects the strongest casemates which were built to stand the biggest calipers shots. Along with the frontal plate, there may be vertical steel girders enhancing the side walls of the firing chamber and iron beams very often reinforce the concrete ceiling. As for the structure and the dimension of the firing chamber, if the weapon was a heavy machine gun, the plan can be approximately trapezoidal or rectangular. If trapezoidal, the frontal wall ranges around 110-120 cm, the back parallel wall is about 150 cm, while the depth ranges around 115 cm. Not so comfortable a place! If the firing chamber plan is rectangular, the longer side (with the opening) is about 3 metres, while the depth is about 0,8-1 meter. Firing chambers hosting anti tank guns were wider and deeper. They have larger nearby compartments and their plan is approximately an oblong trapeizoid.
Along with the firing chamber there is a short corridor connecting the firing chamber with an inner veritical shaft or whatever a passage (a corridor, a flight of upward stairs) linking the weapon position to the logistical part of the work. Somewhere along the corridor or near the logistical part there may be other recesses used for manifold purpouses.
The firing chamber is completely sealed off the rest of the work by an airtight closure steel door. Moreover, the angular disposition of the weapon chamber, with regard to its access, is such to minimize the effect of the eventual explosion of the firing chamber itself thus protecting the rest of the defensive work.
Speaking of casemates in general terms would require to stop the speech at this point since giving more details seems absolutely impossible. It means that the variety of adopted solutions is so huge that giving more details would mean just describing case by case what can be seen along different sectors of the wall and this would not fail in bothering the patient reader.
Few more things infact can be said in general: the bigness of the casemate and the thickness of the concrete walls depeded on how heavy shots the casemate was supposed to stand. It follows therefore that the lower the altitude the stronger the casemates.
No need to say that casemates adopt all the camouflaging methods described somewhereelse in this document. It is sometimes hard even to point out a casemate since not only can it be completely camouflaged by additional layers of concrete and thrusted stones, but, as already said before, it looks as almost completely buried being covered by stones, rocks or earth so as to make it hardly distinguishable on the terrain. On the contrary, a casemate is fully visible when the camouflaging was not completed and in this case it reveals its concrete core walls.
Casemates can be huge concrete parallelepipeds about 7 x 5 metres (measured when naked: without the supplementary layers required by camouflagings). They can be huge cylinders or rounded shape solids or flat boxes slightly protruding from the terrain and built against a slope.
A different solution was adopted for 7000 positions whose casemates often were hastly left naked and fully visible.
The thickness of the concrete walls can range from 1-1.5 metres of the mountain casemates to 2,5-3,5 metres of the lower altitudes defensive works. Where the massive concrete walls were also reinforced by iron poles, the thickness was smaller: judging anyway from what remains of some exploded casemates, the concrete was not always reinforced.
In most cases, the casemate structure seems imponent and somehow over sized but its dimensions and the concrete walls thickness were for certain chosen and planned with strict regard either to the caliper bigness the defensive work was supposed to stand, or the required firing action (frontal or lateral).
As mentioned before, being the casemate roof protected by a massive bunch of rocks and earth, it looks partially buried with the fire openings nearly placed at the ground level. Embrasures are protected from direct or rebounding shots or splinters by the typical structure recalling a hopper. The outward splaying has a vertical frontal section which generally is flat and braod even if it can also be a less smashed rectancle regardless of whether the steel plate and armor are mounted. Armored frontal walls have very small weapon openings (about 20cm side square). Where there was no armors, the embrasures are in general much wider. In these cases, they may have been closed by iron windows preventing any entries during inoperative times.
The casemate is a combat block with one position. But in many cases, more than one positions are gathered in groups of two or three to form a more complex structure. A block infact has two or more positions.
The common situation in which the block has two weapons is called "malloppo binato"which could be translated by something like "twin block".
Two types of combat blocks can be observed: a combat block with just one firing chamber (with two or more positions inside) and a combat block with separate firing chambers (so many chambers as positions).
Combat blocks with one firing chamber are not as common as those with separate firing chambers. The single firing chamber is a room of suitable bigness and structure with as many weapon basements as the positions. The block plan is variable and depends on the type of weapons, their number, the covered sectors and, above all, the terrain. Generally has each position its small ammunition deposit, a recess for exausted machine-gun cartridges cases and separate tubing for shooter and servant.The most common case is a combat block with separate firing chambers. In this case very solid concrete walls separate the firing chambers from each others. Each firing chamber has its sealing steel door. Common is the case in which the firing sector of a weapon is 90 or more degrees from the sector of the other weapon and it may happen that the actions of two weapons were exactly opposite.
In case of separated chambers, there may be a short corridor inside the combact block connecting the firing chambers. Each firing chamber is totally independent from the others.
A rule which wasn't yet confuted, at least for these sectors of the wall, is that in case of separated twin chambers block, there is always an emergecy exit in the combat block itself. There may be a series of upward steps and the short corridor has the usual bayonet bend. The passage broadness is slighly smaller then internal corridors and a steel door is present at its mouth.
The disposition of the combat blocks was very variable and depending on the weapons, the physiscal structure of the terrain and the sectors to beat.
Blocks are very common in eastern Vallo. Nothing in general can be said about their looking: they may have any shape and height depending on the weapons placement and the terrain. Sometimes do they look like huge truncate cones or smashed cylinders: more often, like casemetes, their shape is indefinable.
Many casemates and blocks underwent damage or destruction by explosive during the years of the cold war or just after the second world war. Jugoslav army took away every steel or iron device and tried to delete every possible sign recalling the italian administration of western Jugoslavia from 1919 to 1943-45. Lighter blocks and casemates have been swept off, but the heaviest ones suffered little damage. The reason why most standed these destruction attempts is not only the impressive hugeness of the blocks themselves, but it could be perhaps explained by their inner structure. The underground system from which vertical linking shafts begin and the upper block are not two separate structures by they come from the same massive concrete layer. So, the block shape one can see on the surface is just the iceberg top because the same shape is kept underground and it deeply goes down to the underground sector of the defensive work. So the block structure is not limited at the surface but it was got by a single concrete layer filling an enormous vertical hole dug in the rock and as deep as the linking shaft.
|Accesses to positions
Being the logistical part the deepest structure of the work, most of the positions on the surface were reachable by more or less steep and long flights of upward stairs.
In many cases, the combat blocks were directly connected to the inner compartments by a vertical shaft which may have been as high as required by the depth of the underground part (8-10-12 metres or more). Soldiers had to climb up the shaft to reach the blocks on the surface.
The shafts have approximately square or circular sections. If the shaft is square, its upper mouth is flush with the upper foor and it's open (sometimes with a trap door) just behind a firing chamber. If the shaft is circular, its upper opening is a vertical door linking the shaft with the corridor between the firing chambers. The passage is protected by the usual steel door sealing off the combat block.
The circular shaft was where circular iron stairs were placed: the iron structure had a central vertical pole on which the steps were welded. The circular stairs were sustained by vertical iron poles which were thrusted on the concrete walls of the shaft. The last and highest step was indeed a reinforced concrete platform. The central iron pole was bent at the platform to make a sort of protective railing. Electrical power lines and the fresh air distributing tubes ran vertically up the inner walls of the shaft. The shaft diameter is about 150 cm. In some cases the whole round stairs and central pivot were made by reiforced concrete.
If the shaft is square, an inside ladder was got by iron clamps thrusted into the concrete walls. The section is almost square but it is slightly smashed to make the climbing more comfortable (about 80cm (width) x 90-100cm (depth)).
If the position is in a casemate, the shaft is generally square. Blocks with two or more positions generally have a circular section shaft which was somehow more comfortable being broader than square one. There may also be a square shaft serving a block with two positions and emergency exit, but, in this case, the shaft section is bigger than the section of a square shaft connecting a single position.
Circular stairs steps were low enough to facilitate the upward carring of weapons parts and ammunitions. On the contrary, in case of shafts with square section, remains of rails on which manual lift are likely to have been working, are still visible.
To Chapter III