from the book 'Many Fronts'
'Blowing Up the Castelletto'
edited by Lewis R. Freeman

Alpine Operations

map of the area


It was about the middle of last July that the laconic Italian bulletin recorded, in effect, that the blowing of the top off a certain mountain in the Dolomite region had been accomplished with complete success, and that a considerable extension of line had been possible as a consequence.

That was about all there was to it, I believe; and yet the wonder engendered by the superb audacity of the thing had haunted me from the first. There was no suggestion of a hint of how it was done, or even why it was done. All that was left to the imagination, and the result—in my own case at least—was the awakening of a burning interest in the ways of the warriors who were wont to throw mountain peaks and fragments of glacier at one another as the everyday plains-bred soldier throws hand-grenades, which, waxing rather than waning as the weeks went by, finally impelled me to attempt a visit to the Austro-Italian Alpine Front at a time of year when the weather conditions threatened to be all but, if not quite, prohibitive.

"With twenty-five degrees of frost at sea-level in France," observed a French officer at Amiens to whom I confided the plan, " what do you expect to find at 10,000 feet on the Tyrol?”

"A number of things which they don't do at sea-level in France or anywhere else," I replied, "but especially why they blow the tops off mountain peaks, and how they blow the tops off mountain peaks."

Even in Rome and Milan (though there were some who claimed social acquaintance with the Titans who had been conforming Alpine scenery to tactical exigency), they still spoke vaguely of the thing as "fantastico" and "incredibile," as men might refer to operations in the Mountains of the Moon.

But once in the Zona di Guerra, with every rift in the lowering cloud-blanket that so loves to muffle the verdant plain of Venezia in its moist folds revealing (in the imminent loom of the snowy barrier rearing itself against the cobalt of the northern sky) evidence that the "mountain-top" part of the story had at least some foundation of fact, whether the "blowing off" part did or not, things took on a different aspect. On my very first day at General Headquarters I met officers who claimed to have seen with their own eyes a mountain whose top had been blown off; indeed, they even mentioned the names of the montagna mutilati, showed me where they were on the map, pointed out the strategical advantages which had already accrued from taking them, and those which might be expected to accrue later.

They were still there, I was assured, even if their tops had been blown off. They were still held by the Alpini. Two of the most important of them were not so far away; indeed, both could be plainly seen from where we were—if other and nearer mountains did not stand between, and, of course, if the accursed storm-clouds would only lift. And so, at last, the names of Castelletto and Col di Lano took sharpened shape as something more than mystic symbols.

"But can I not go and see them?” I asked. "You have told me why you blew them up, but not how; yet that is the very thing that I came out to find about at first hand."

They shook their heads dubiously. "Not while this weather lasts," one of them said. "It has snowed in the Alps every day for over a month. The valangas are coming down everywhere, and (even if you were willing to risk being buried under one of them) the roads in places will not be open for weeks. You might wait here a month or so, and even then be disappointed so far as getting about on the Alpine Front is concerned. Best see what you can of the Isonzo Front now and come back for the Alps in the spring."

That seemed to settle it so far as seeing the Castelletto and Col di Lano was concerned. Regarding the way in which they were mined, however, one of the officers at the Ufficio Stampa said that he would endeavour to arrange to have the Castelletto—much the greater operation of the two—report put at my disposal, as well as a set of photographs which had been taken to show the progress of this mighty work.

"We have never given out any of the photographs before," he said, "and only portions of the report; but since you came to Italy on purpose to learn about the mountain whose top was blown off, the Comando Supremo may be moved to make a special dispensation in your favour."

Exclusive permission to make use of both report and photographs was granted me in due time, and since the former makes clear both the "why" and the "how" of the unprecedented Castelletto operation, it will perhaps be best to summarise it first as a sort of drab background for the more vivid and intimate personal details which a lucky turn of the fitful weather vane made it possible for me to obtain later.

The first part of the report, by the Colonel commanding the Alpini Group, makes plain why the mining of the Castelletto became a sine qua non to further progress in this important sector.

"In the month of October, 1915." he writes, "I was charged with the carrying out of an attack with two battalions of Alpini against the positions of Castelletto and Forcella Bois. This was the fourth time, if I am not mistaken, that an attempt on these positions had been made. In spite of the fact that the artillery preparation of the opening day had been excellently performed. I discovered, on the evening of October 17, when I moved with my troops to the attack, that its work had been absolutely of no avail.

"Having received orders at midnight to proceed to Vervei, where the two battalions above mentioned were to take part in another operation, I was forced to abandon the attack. I am convinced, however, that I would not have succeeded in capturing the Castelletto position."

"As known," the report continues, "the Castelletto is a sort of a spur of the Tofana (about 12,000 feet high), with a balcony shaped like a horse-shoe, and with a periphery consisting of numerous jagged peaks. In the rear of the balcony, and within this rocky spur, the enemy had excavated numerous caverns in which machine-guns and light artillery pieces, handled by isolated but able gun-crews, furnished an invisible and almost impregnable position of defence, giving extraordinary confidence and encouragement to the small forces occupying them.

“Costeana Valley was accordingly at the mercy of the enemy's offence and actually cut in two. From Vervei on, all movements of troops had to be carried on only at night and with great difficulty. The conquest of the Castelletto was rendered necessary not only for tactical but for moral reasons as well, since our troops came to regard it as absolutely imperative that such an obstacle should be overcome. After completing my observations and researches regarding the Castelletto position, I reached the conclusion that the only means of dislodging the enemy therefrom was to blow it up.

"On November 19 I formally presented my plan to Headquarters, and about the middle of December I was authorised to attempt it. The unusual enterprise was a most difficult one, not only on account of its magnitude, but also on account of the particularly unfavourable conditions of the winter season. Having prepared the necessary material for construction and excavation work, I began, on January 3, 1916, fortifying the position (entirely unprotected at the time) from which we would have to work, and completing the construction of the necessary buildings.

"Second Lieutenant Malvezzi, in his report on the subject, describes concisely and modestly the development of the work. The accomplishment of the enterprise, considered by many as chimerical, is due not only to the technical ability of Lt. Malvezzi, and Lt. Tissi, his assistant., but to their special military qualifications as well; also to the courage and goodwill of the Alpini who, in a very short time, became a personnel of able miners and clever mechanics.

"The vicissitudes during more than six months' work, at a distance of only a few metres from the enemy, and under an incessant artillery fire and shelling by bombardas, could well form the subject for a book devoted to the study of character. Although fully aware of the attendant dangers, including those of falling rocks due to the counter-mining of the enemy, the Alpini of the Castelletto, during the period of more than six months, gave proofs of brilliant valour and unflinching perseverance. They were calm at all times, and moved only by the spirit of duty.

"In transmitting to Your Excellency the enclosed copy of the report compiled exclusively by Lt. Malvezzi (Lt. Tissi is at present lying wounded in the hospital), I desire to recommend to you these two officers (both as excellent engineers and brave soldiers), as well as the Alpini who were co-operating with them. Without any exaggeration, I consider their achievement as absolutely marvellous, both on account of the great technical difficulties surmounted and the military results obtained. The Austrian officers taken prisoner unanimously confirm the fact that only by springing a mine could the Italians have taken this position so important to the enemy."


Lt. Malvezzi's appended report launched at once into the how of the titanic task which was set for him.

"On January 3, 1916," he writes, "work was begun on the approach to Castelletto, on the Tofana di Roches slope, levelling the soil and enabling the construction of lodging quarters for officers and troops. This work required the cutting of 660 cubic metres of rock. Next the construction of quarters, and the concealing them was quickly accomplished. Finally, there was garrisoned at this post the Castelletto Detachment, commonly called the 'T. K.,' consisting of the necessary personnel for labour and the defence of the position.

"Our first work was to examine and disclose the enemy lines of communication about the Castelletto and Tofana sides, and to gain full knowledge of their position in detail. In order to accomplish this, observation points were established which allowed us to carry out such investigation and to make topographical sketches of the zone. Being as we were always in the proximity of the enemy, this was a long and fatiguing work. After a month, however, we succeeded in constructing a series of positions at short distances from those of the enemy (from 50 to 150 metres). These were provided with cables and rope ladders to enable us the more rapidly and easily to study (from all possible points of vantage) the enemy's positions and the development of his works.

"The topographic work was begun by taking as a plan metric base measurement 116 metres of ground on a four-triangle table, which method enabled making all other drawings based on it. By basing our findings on this table, we were able to draw up a series of points of the enemy's positions. Using the method of successive intersections, we thus obtained all points of interest to us, as regards direction, distance and height.

"In addition to this work, executed with the greatest care and accuracy, we made two independent drawings of the enemy's positions by simpler but less exact methods. The first was made with a topographic compass and Abney level; the other with a Monticole field-square. By these means we obtained excellent checks on the base system, and so grounded our work entirely on the trigonometric table and on the drawings by intersections.

"From the middle of February to the end of March the tools used for piercing consisted only of mallets and chisels. Our progress was necessarily slow, yet it was sufficient in this time to give us, besides 14 metres of tunnel, room for installing the perforating machinery. At the end of March, notwithstanding heavy snowstorms, the machinery—some pieces of it weighed as much as 500 and 600 kilos—for beginning work was installed. This was all brought up by hand, and without incident.

"The mechanical work was begun on April 2. We utilised two plant as follows:

"(1) A complete group of benzo-compressors, consisting of a 30-40 horse-power kerosene motor adjusted to a Sullivan compressor by means of a belt. This machinery was installed, on a solid base of cement, at the beginning of the tunnel, in a 5 X 8 metre space dug out in the side of the mountain for that purpose.

"(2) An Ingersoll compressor mounted on a four-wheel truck.

"Both machines were of American manufacture and gave complete satisfaction at all times. Each compressed the air to a density of about seven atmospheres, injecting it into an air-chamber, whence, by means of a rigid tube, ending in one of flexible rubber, it was conveyed to the respective drills.

"Four squads worked at a time, each one consisting of a foreman and from 25 to 30 miners. Each squad worked six hours without interruption. This shift, apparently light, was found, on the contrary, to be very heavy, owing principally to the development of nitric gases which poisoned the air, and to the dust caused by the drills.

"At first the only explosive used was military gelatine; later, dynamite-gelatine. The system of over-charging the holes was always adopted, in order to reduce the debris to minute particles, easier to be transported and unloaded. The work was carried on in sections, varying from 180 by 180 metres to 2 by 2. The flat stretches of the tunnel were laid with Decauville rails. All material was carried out in cars and dumped into a hopper discharging into a large pipe. (The dump was accumulated at a point beyond the observation of the Austrians.) The average rate of progress was 5-10 metres per day."

It may be well to explain here that it was not possible to begin tunnelling on the same level at which the mine was to be exploded, but considerably more than 150 feet below that level. The tunnel, had, therefore, to be driven on a steep gradient. Another point which the report does not make clear should be borne in mind, viz. that the tunnel divided in the heart of the Castelletto. the main bore being driven on to where the mine was to be exploded, while a smaller branch—referred to below as the "Loop-holed Tunnel"—was run up to a point where favourable exit could be obtained for charging into and occupying the crater of the exploded mine. In all 507 metres of tunnel had to be driven, involving the excavation of 2,200 cubic metres of rock. The details of this work are given in the report as follows:

(A) Chamber for Sullivan Compressor: Dimensions: 5x8 metres; average height 2-20 metres.

(B) First part of gallery to second dump of material. Length 72 metres; inclination 38- 70 per cent.; elevation gained 25-90 metres.

(C) Second dump of material, established in order to free space for further work and reduce the length of transportation.

(D) Ingersoll Group chamber. Dimensions: 4\x 6-50 metres; average height 2 metres.

(E) Cut from the gallery of the second dump of material to the beginning of the ascent to the mining chamber. Length 136 metres; inclination 70 per cent.; elevation gained 6-40 metres.

(E) Ascent to mining chamber. Length 22 metres; inclination 36-30 per cent.; elevation gained 10-75 metres. (This ascent, in order to facilitate tamping, was worked by dividing it into three sections of 1 X 160 metres, at nearly right angles.)

(G)Mining chamber. Dimensions: 5 X 5-50 metre!; average height 2-30 metres.

(H) Loop-holed tunnel. Length 162 metres; inclination 60 per cent.; elevation gained 83-50 metres in this tunnel itself, or a total of 168-50 from the second dump. This tunnel (the one though which the men were to pass for the attack after the explosion of the mine) had to be strictly confined to the rocky stratum between the Tofana and the Castelletto; its planimetry appears (see map), therefore, rather uneven due to the constant elevation of the rock.

(I) Line of communication—partly in a natural cavern—measuring about 250 metres in length/ and giving access from the lodging quarters to the works.

(J) Tunnel dug out to the extreme south end of the Castelletto. 30 metres long, with two portholes (each 4 metres wide) for two Depfort gulls, with closed cavern for the guns and ammunition. It was originally intended to divide the explosive charge between two chambers, each having a mining line of resistance of 20 metres with a 16-ton explosive charge of 92 per cent. gelatine. However, owing to the countermining work carried on by the enemy—we were only a few metres from one of his positions during the charging of the mine chamber—we were obliged to confine the entire charge to a tingle chamber.

"The enemy, meanwhile, with a view to avoiding the effects of our mine beneath the peaks of the Castelletto, had transferred most of his shelters to the side of the Tofana a\ d the Selletta. This necessitated a considerable alteration in the location of the mine as originally planned, in order that it should act against the enemy shelters on both the Castelletto and Tnfana flanks.

"The charge was computed on a basis of minimum resistance of 20 metres, taking into consideration the nature of the rock (which was fissured) and the existence of numerous splits and caverns. The co-efficient of overcharge was, therefore, rather high. In order to obtain the maximum effect under these conditions, only 92 per cent, explosive nitro-glycerine was used. The total charge was 35 tons.

"The method of priming adopted was suggested by Lieut.-Col. Tatoli, of the Engineers Corps. This consisted of five priming groups, each of three friction tubes. One of the groups ran along the central axis of the chamber, while the other four, parallel with the first, were disposed symmetrically facing the four corners of the chamber. Each tube (12 inches inside diameter by 4-50 metres in length) was alternately charged with gelatine and gun-cotton and pierced by picric acid detonating fuse, ending in a gun-cotton cartridge with electric percussion cap. In the very centre of the charge there were inserted two cases of gun-cotton, with electric percussion cap and detonating fuse, with a view to securing a second springing of the mine to follow the first.

"We thus had in all seventeen electric circuits divided into three groups, each formed by the circuits of five tubes, connected with the five groups of friction tubes. Two of these electric groups were composed of six circuits each, by adding the two circuits of the above-mentioned cases containing the gun-cotton. Each of these electric groups ended with a Cantone exploder, placed at about 450 metres distance from the mine-chamber.

"The tamping was effected with cement and with sandbags, with heavy wooden beams between the latter. It was made more effective by dividing into sections at right angles to each other. The theoretical length of the tamping was 25 metres.

"The charging of the mine chamber began July 3, 1916, at 5 p.m., and was completed at 3 p.m. of July 9 this work including tamping, priming and laying of electric circuits. The final connections between the latter and the exploders, by means of wires suspended in the air, were made on July 10. The mine was sprung on July 11 at 3.30 p.m., and responded fully to our calculations and expectations." (Signed) L. MALVEZZI.

2nd Lieut. 7th Regiment Alpini."


A week of unspeakable weather went by—an interval the days of which I spent among the "Cave-men" of the Carso and the nights of which were largely devoted to puzzling through the mysteries of the Castelletto report with the aid of my Italian dictionary—and then the unexpected miracle happened. Rain and snow ceased, the sky cleared, and a spell of sparkling days succeeded the interminable months of storm and lowering clouds. From the high Alps came word that the grip of the frost had paralysed the avalanches for the moment, and that rapid progress was being made in opening up the roads for traffic.

"Now is your chance to see the Castelletto," they told me at headquarters. "If you start at once you ought to be able to get through without much trouble; and, if the weather holds good, you may even be able to get back without long delay, though on that score you'll have to take your chances. Doubtless they will be able to get you out in some way whatever happens." And so it chanced that on a diamond-bright morning in early January I found myself, after a couple of days of strenuous motoring, speeding in a military car past the old custom-house and up into the heart of that most weirdly grand of all Alpine regions, the Dolomites. Already we were well over into what had once been Austrian territory, and the splintered pinnacles which notched the skyline ahead of us were, as my escorting officer explained, held in part by both the Italians and the enemy. As we coasted down into Cortina di Ampezzo— which in its swarming tourist hotels of motley design rivals St. Moritz or Chamonix— Capt. P------ pointed to where a clean-lined wall of snow-capped yellow rock reared itself against the deep purple of the western sky.

"That high mountain ridge is the Tofana massif." he said, "and that partly isolated mass of lighter-coloured rock (crowned with towers like a mediaeval stronghold) at its further end is what is left of the famous Castelletto. It is twenty kilometres or more away, but you can see even from here how it dominated the valley and road, the latter the much-pictured Dolomite road, which is also a route of great military importance.

"Now look at the end of the Castelletto toward the wall of the Tofana. Do you see where it seems to have been sliced off smoothly at an angle of about forty-five degrees? Well, that is the part they blew off last July. Up to then that end like the other, was crowned with a lofty spire. That spire, the base from which it sprung, the Austrian barracks and munition depots, together with the men stationed there —all were blown up and destroyed in the explosion.

"Take a good look at it while you have a chance, for the skyline view is better from a distance than from close at hand, where we shall go this afternoon if the way is open. To see the effect of the explosion at its best," he added, "one should look at it from the Austrian lines, as it was the blowing out of the other side of the mountain which undermined and let down the top. If you come back here in the spring doubtless we will be in occupation of a number of interesting observation points over there."

Viewed even from a distance of a dozen miles or more the alteration wrought in the skyline by the explosion was not difficult to imagine. It was, indeed, literally true— what I had never been fully able to make myself believe until that moment—that a mountain peak had been blown off—hundreds of feet of it, and thousands of tons. My eyes remained focussed in awed fascination on the unnaturally even profile of the wound until our snorting car skidded round a bend of the frozen road and the thick-growing pine forest shut it from sight.

It was not until, after ten miles of precarious climbing and clawing up the ice-paved, snow-walled road, our car brought up in the midst of a neat little group of Alpine buildings nestling in the protection of the last of the timber, that Capt. P------revealed the surprise that had been prepared for me.

"Our host here," he said, "will be Colonel X------, who conceived and directed the Castelletto project, and at dinner to-night you will meet, and can talk as long as you like, with Lieutenant Malvezzi, who did the work. He is still quartered here, and will be glad to tell you all that he can about Alpine military engineering. We have already sent him word that you came to Italy expressly to see him."

After a hasty lunch Capt. P------and I, accompanied by an officer of Alpini from the camp, started for the Castelletto. Our powerful military car, which, in spite of the fact that it had non-skid tyres, had been giving a good deal of trouble on the ice, was left behind, and a smaller but heavily-engined machine, with sharp spikes clamped over the rims to grip the glassy surface of the road, was taken for the few miles of the latter which were still open. Abandoning this in a snow-bank at a little advanced camp well up under the towering wall of the Tofana, we took our alpenstocks and started on the 2,000-foot climb up to the base of the Castelletto.

The hard-packed snow on the thirty to forty degree slope must have averaged from ten to twenty feet deep all the way, while, for a half-mile or so midway, it was humped up in crumplec fold where, a fortnight before, one of the largest and most terrible slides ever known in the Alp had plunged down on its sinister mission to the bottom of the valley. The full story of that avalanche will hardly be told until after the war.

Slightly softened by the brilliant sun, the snow gave good footing; but even so it was a stiff pull to the little ice and rock-begirt barracks at the base of the cliff, and I gained some idea of the titanic labour involved in getting guns munitions, machinery, food, and thirty-five tons of high explosive up there, all by hand in every sort of weather, and much of it (to avoid enemy observation and fire) at night.

Midwinter was not, of course, the time to see anything of the real effects of the great explosion, for the huge crater torn by the latter was drifted full of snow, and snow was also responsible for the complete obliteration of the countless thousands of tons of debris that had been precipitated down the mountain side. A dizzy climb up the ladder-like stairway, and a crawling clamber through a hundred yards of the winding tunnel from the rock chambers which had housed the compressors, revealed about all that was visible at the time of the preparations and consequences of the mighty work; but a peep from the observation port of a certain cunningly concealed gun- cavern discovered a panorama which gave illuminative point to the concluding words of the artillery officer who, pointing with the shod handle of an ice-pick, explained the situation to me from that vantage.

"So you see," he had said. "that the Castelletto in the enemy's hands was a stone wall which effectually barred our further progress; while in our hands it becomes a lever which— whenever we really need to take them—will pry open for us positions of vital importance. We simply had to have it; and so we took it in the one way it could be taken.


Save for his Alpini uniform Lieutenant Malvezzi, when I met him at dinner that evening, might well have passed for the typical musician of drama or romance. His skin and hair and eyes were dark and his long nervous fingers flitted over the paper on which he sketched various phases of the Castelletto work very much as those of a pianist flit above his ivory keys. The dreamy, far-away look in his eyes was also suggestive of the musician, but that I had long come to recognise as equally characteristic of all great engineers, the men whose tangible achievements are only the fruition of days and nights of dreaming.

"Where shall I begin the story?” he has asked as the diners in the regimental mess begar to resolve into little knots of threes and fours over coffee and cigars; and I had suggested that he take it up where his report left off. "That stopped just as things began to happen " I said. "Now tell what did happen."

The Tenente laughed a laugh suggestive of rueful reminiscence, and a smile ran round among those of the officers who had heard and understood my words. "So far as I am concerned." he replied, "that covers about five minutes of activity—five minutes for which we had been preparing for six months. You understand that we had constructed a branch tunnel through which our men were to rush and occupy the crater as soon after the explosion as possible.

"Ecco. The men were all massed ready on and under the terrace, and nothing remained but the making of the connection firing the mine. I took one long look around and then threw over the electric switch closing the circuit. Every one seemed to be holding his breath as he waited. One two, three seconds passed in a silence so intense that I heard the sharp 'ping' of the water dripping from the roof of the chamber and striking the pool it had formed below.

"Then, before any other sound was audible, the whole mountain gave a quick convulsive jerk, strong enough to throw some of the men off their feet. A heavy grinding rumble in the earth came with a shivering that followed the jerk, but the real roar of the explosion (from the outside) was not audible for a second or two later. Only those watching from a distance of several kilometres saw the right-hand pinnacle of the Castelletto give a sudden heave, and then sink out of sight in a cloud of dust and smoke.

"In addition to the honour of firing the mine that of leading my men into the crater had also been reserved for me, and as soon as I heard the roar of the explosion I gave the order for them to follow me up into the tunnel. Well ------" he paused and ran his laughing eyes around the grinning circle of his fellow officers, "that is about as far as my evidence is good for anything. As I went clambering up the slippery steps of the tunnel an almost solid wall of choking fumes struck me in the face, and I—and all of my men except those near or outside of the portal—dropped coughing in my tracks."

"Had the mine blown back through the tamping?” I asked.

"Not exactly," he replied, his rueful smile becoming almost sheepish, as of one who had allowed himself to become the victim of a prank. "The Austrians had a big store of asphyxiating bombs on hand to use against us, and these, exploded by our mine, vented their spite on friend and foe alike. We were not able to occupy the crater for twenty-four hours.

"I am glad to say that I spent what would otherwise have been an intolerably anxious interval unconscious in the hospital. By the time I had been revived a friendly breeze had thinned the gas sufficiently to allow our Alpini to move into the crater and reap— in spite of the delay—every advantage we had at any time counted upon from the operation. Our most cherished capture was the ' perforator'—practically intact—with which the Austrians were driving an almost completed counter-mine directly under us."

"The nervous tension must have been rather strong toward the end, wasn't it?” I asked; "especially when you knew the enemy had at last got your work definitely located and was rushing his counter-mine?”

The smile of whimsical ruefulness died out of the dark sensitive face, leaving behind it lines I had not noticed before—lines that only come on young faces after weeks or months of incessant anxiety. The backward cast shadows of a time of terrible memory were lurking behind his eyes as he replied:

"For seven days and nights before the mine was sprung neither I nor the officers working with me slept or even rested from work."

That was all he said; but I saw the eyes— brimming with ready sympathy—of his fellow officers turn to where he sat, and knew the time for light questionings was past. Not until that moment did a full appreciation of the travail involved in the blowing up of the Castelletto sink home to me, and I nodded fervent assent to the words of the English-educated Captain of Alpini next me when he observed that "Malvezzi's little 'Order of Savoie' was jolly well earned, eh?”


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