Midget submarines have been almost forgotten in these days of giant nuclears. This may be because the midgets formed what amounted to a private navy and few people knew its value. Perhaps, also, those of us who were privileged to serve in X-Craft or the like did not always appear to take life as seriously as modern navies demand. In turn, it may be that modern navies after the war felt unable to think very seriously about midget submarines. Whatever the reasons may have been, the Royal Navy disbanded its small X- Craft Unit ten years ago and thereby lost an extremely potent, yet inexpensive, weapon system.
It seems worthwhile now, when we are trying ever more urgently to get good value for our money and improve the effectiveness of our weapons systems, to re-examine the concept of midget submarines. Past experience, coupled with the nature of the present threat, suggests that they might solve some of our problems rather cheaply.
Our foremost problem in the navy is still the enemy submarine, which has now added missiles to its armory and thus poses an air as well as an underwater threat. Submarines are still undeniably difficult to sink at sea, even with the most modern antisubmarine warfare devices. Their ability to use nuclear power and to deliver attacks from very long range makes ASW even harder. In the open ocean the submarine nearly always holds the initiative: it selects the time, the place, and the conditions for its attack. If, however, we ourselves could choose when and where to bring the enemy submarines to action, the engagements might more often end in favor of the ASW forces.
There are two reasonable places to kill wasps. They can either be swatted while they buzz around a honey pot or they can be destroyed in their nest. The first method is apt to be expensive both in honey and effort; in terms of cost-effectiveness, it is better to kill wasps in their nest. Incidentally, anyone who tries to hit wasps en route from nest to honey pot will soon discover that the attrition rate is low and the hunter is exposed to surprise flank attacks from his quarry.
In ASW, as in wasp-hunting, there are two reasonable places to seek and kill the enemy: in a focal area to which he is attracted (the convoy honey pot for example) or at his base before he sails. The difficulties of ASW around a convoy are all too familiar, but the feasibility of carrying ASW into enemy harbors has scarcely been considered.
There are several ways in which submarines —or surface vessels—might be attacked while alongside piers or tenders. It is assumed that nuclear, biological warfare and chemical warfare weapons will be prohibited, but, even if they are allowed, their delivery by air or missile may be ineffective against an enemy dispersed in remote anchorages from which he can sail and submerge at very short notice. Conventional bombing is unlikely to succeed in the face of modern anti-aircraft defenses. Air or missile attacks are not therefore favored. Another possible weapon carrier— the swimmer—is discounted because he must be transported to within a few hundred yards of his objective. This is always difficult and often impossible. Moreover, swimmers can carry only small quantities of explosive.
Midget submarines, however, offer significant advantages over the other conceivable methods of attack. The British X-Craft was able to carry enough limpet mines to sink several submarines or small ships or, alternatively, it could carry two two-ton time-fuzed ground mines for placing under larger ships or installations such as cruisers or floating docks. The effectiveness of these craft and their high kill or success probability in a wide variety of operations was fully proved during the last war. They disabled the pocket battleship Tirpitz in Altenfjord and the cruiser Takao in Singapore; sank the floating dock in Bergen; cut the underwater telephone cables between Saigon, Hong Kong, and Singapore, and marked the approaches to the landing beaches in France on D-Day. They were highly versatile and powerful submersibles; yet their cost was very small and they required a crew of only four or five.
There were various breeds of midget in the different World War II navies. They included British and Italian Chariots (or Human Torpedoes); German “Marten,” “Newt,” “Beaver,” and “Seal” craft; Japanese torpedo launchers; and the British X- Craft. All of these achieved their aim to a greater or lesser degree. Only the British X- Craft however, were independent in the operational area. All the others were in some way constrained by circumstances. For example, if the tide was found to be unfavorable or if intelligence had erred, the mission was usually aborted; it was seldom possible to change the plan and re-attack. Furthermore, all except the X-Craft had to be launched within a few miles of the enemy; the parent vessel risked much and would risk more now.
The X-Craft were released by the towing submarines a long way from their targets; they had a range of several hundred miles, and their chances of success and evasion were much higher than their smaller relations.
What were these X-Craft like? The postwar British Shrimp class, now scrapped or sold, displaced some 35 tons on the surface. Its 50-foot length was divided into four compartments: the battery compartment forward; the wet-and-dry chamber or diving lock which also contained the head and served as an access hatch; the control room; and, right aft, the engine room. The average diameter was about six feet.
Each craft could be hauled up a slipway and quickly parted into three sections if required for maintenance. The complete craft was small enough to be loaded onto a railway truck, however. Rail was, in fact, the best method of transport from one base to another, although it gave rise to some unlikely situations. The crew travelled with their craft and soon found that engineers were a congenial lot, quite willing to meet the submariners’ eccentric wishes. Trains were known to stop in order to allow the crew to hunt pheasants, hold parties in favorite hostelries en route, and make various purchases to ensure their wellbeing when the train was underway. It was not always easy to persuade the railway police that a crew, returning from one of these sorties to a marshalling yard in the middle of England, were rejoining their submarine on a railway siding.
The other, more warlike, method of transport—towing—was understandably less popular. A passage crew of four manned the craft during a tow and were relieved by the operational crew only when the tow was slipped at the edge of the operational area. The task of the passage crew was envied by none. Even though the tow could be made at an average speed of about ten knots, with the parent submarine and X-Craft both submerged, it could last for many days. The passage crew had, during this time, to exist in appalling discomfort while making sure that everything was in perfect condition for the operational crew of five (the extra member was needed as a diver) who, of course, had most of the excitement and rewards. Naturally, the operational crew also had most of the hazards, but the passage crew were not entirely without these. If, for instance, the heavy tow rope parted, its weight could take the craft rapidly to the bottom.
In tow, the craft oscillated gently up or down through a hundred feet or more; it was unwise to try towing submerged in shallow water. Eventually the planesman learned to recognize whether an oscillation was normal or whether it signified that the trim or hydroplanes were wrongly set. Inexperienced operators made continual adjustments; older hands touched the controls perhaps only once a watch. Naturally, everyone going on watch made one small adjustment to indicate that hitherto the trim had been in error but was now satisfactory in his care.
Every two hours the towing submarine called the passage crew by telephone—if the telephone worked. Its cable was made up in the tow rope; a few contortions of the latter when leaving harbor were enough to ensure that communications would be non-existent for the remainder of the tow. This, to say the least, was tiresome. Life for the passage crew then became a series of surprises.
Every six hours the midget was brought up to “guff through,” changing the stale air by raising the induction mast and running the engine for ten minutes—or longer if the battery and air bottles had to be recharged. In rough weather this was an especially miserable period.
In passage, time soon ceased to have any meaning. This was merciful under the circumstances. The two men on watch were supposed to be relieved by the others every two hours, but sometimes they stayed on watch in a sort of stupor for three, four, or even six hours. This was principally because they had padded seats and were relatively comfortable; off watch there was only the engine to lean against or the periscope to coil around although some craft had a primitive and wholly inadequate bunk. Any real sleep was almost impossible. When the men off watch had no work to do, they simply slipped their minds into neutral and hoped that time would pass. For much of the time, however, they had to work hard. At least this helped to keep away the cold—a damp, grey, almost tangible variety that no kind of clothing could keep out. There were electrical insulations to be checked; equipment to be tested; bilges to be dried; machinery to be greased and oiled; records to be written up; the whole craft to be kept scrupulously clean (a matter of particular pride); and the food-—such as it was— to be prepared.
There was, of course, no galley. A carpenter’s glue-pot in the control room served as a double boiler; an electric kettle provided hot water. For the first 24 hours of a long tow some attempt was made to cook meals. That is to say the first four tins which came to hand were emptied into the glue-pot, stirred and heated. The resulting potmess was then eaten with spoons out of soup plates. It was not an attractive meal but its memory remained until the next guff through; its smell pervaded the boat and condensation trickled drearily down the inside of the pressure hull. It was difficult to be truly thankful for food in these circumstances although one chief petty officer, whose gratitude could only be admired, knelt to say grace before and after each meal. Appetites dwindled rapidly after the first day. Cooked food, biscuits, oranges, apples, coffee, tea, and fruit juice were rejected one by one—generally in that order. A generous government also provided, even in the days of strict food rationing, a large tin of barley sugar, but even this soon sickened.
In peacetime, the passage crew were sometimes let loose by themselves, propelling the craft on the surface by means of its own diesel engine, to visit some hospitable port. The operational crew (who were senior) were prone to arrive later unless the promised warmth of welcome at the port justified the indignity of their making the passage themselves. They generally travelled in the comparative comfort of the X-Craft tender—a small minesweeper of venerable aspect which eventually was retired in favor of a motor fishing vessel of similar antiquity but rather greater reliability.
It was a firm belief of the crews that operations, visits, exercises, inspections, and other naval events—in peacetime at least—should be planned by the crews themselves. It was not in the nature of midget submariners to accept without question rules or plans made by an authority outside the X-Craft family. The crews enjoyed a certain immunity from staff visitations which gave them a justifiable sense of independence. Indeed, it was not unknown for certain measures to be taken to ensure that the staff remained in their offices ashore. It is quite easy in any submarine to discourage visitors; in an X-Craft there was nothing simpler. It will be remembered, for example, that one entered—with considerable difficulty—by way of the head; that one dressed awkwardly and uncomfortably; and that a passenger could only crouch—there was no space for him to sit or stand. Add to these hazards the extremely close company of a crew who perhaps had less than the usual reverence for seniority and who enjoyed steep angles, sudden bottomings and tangling with nets, and it will be appreciated that only those passengers who knew themselves to be friends (the local innkeeper for example) usually ventured out. There were several senior officers who were not deterred, however, and they used to enjoy their trips thoroughly. The Commander-in-Chief Home Fleet once took a delight in flying his flag (borrowed from his official car) from an X- Craft periscope while submerged and circling his fleet in harbor to observe reactions. He subsequently inspected his permanent flagship’s bottom from below and surfaced alongside the gangway. All too few senior officers understood an X-Craft’s capabilities but the realization that more demonstrations were needed came too late.
There were moments when independence made the X-Craft Captain feel a little lonely. He was therefore provided with a radio. Voice communications were no problem, but on occasions he was obliged to use HF CVV; this was a different matter. The Admiralty thoughtfully provided everything necessary, including printed instructions for operating the set, assuming that at least one member of the crew could perform in slow time on a Morse key. No one, however, was so naive as to suppose that the crew of a midget submarine could possibly understand the complexities of naval signalling procedures. Each craft was therefore given a small card, attached to the radio. It described with admirable clarity how an idiot should endeavor to communicate with professional signallers. One three-letter group was particularly useful; it told, in effect, anyone who heard it to be quiet and listen carefully because the sender was inexperienced. Use of this group gave a feeling of power; it probably caused havoc amongst the signal networks of the Fleet.
The X-Craft’s independence was due in no small way to the excellence of its engine. During the war this was a bus engine; in the later craft, the Messrs. Perkins designed a special diesel engine which was very reliable even under the most trying conditions. The craft normally used its engine only on the surface. Air was sucked down an induction mast which also served, rather inefficiently, as a voicepipe for the Captain, who lashed himself to it. It was possible to use the same mast as a snorkel, but since no head valve or remotely operated hull valve was provided, snorkelling was a somewhat chancey undertaking. Rather than snorkel, it was better to trim the craft right down so that its casing was nearly level with the water. The Captain could then lie along the casing and offer only a very small radar or visual target. On peacetime visits, the Captain might elect to stand on his partially submerged and invisible command, rhythmically marking time in a way which gave spectators the impression that he had divine powers to which he was certainly not entitled.
When submerged, the boat, like other submarines, was propelled by its battery. Battery endurance was similar to larger submarines but the available speeds were lower. Cruising speed was about 2 knots and top speed was about 6 knots. Diving depth was nearly as good as that of larger submarines despite the craft having glass viewing ports above and at either side of the command position. External shutters could be drawn across these scuttles, from inside the craft, in the event of depth-charging. The controls were mostly handraulic rather than hydraulic and practically everything could be worked from the First Lieutenant’s position at the after end of the control room. In fact all the First Lieutenant lacked was enough hands and feet. He controlled the trim pump, main engine, main motor, battery charging, auxiliary electrics, and hydroplanes. If the helmsman left his wheel—while helping the diver to dress for example—the First Lieutenant could, by clutching in a secondary wheel, also steer the boat. Course and depth had to be extremely accurate (within half a degree and a few inches respectively) and the Captain, when maneuvering under a target, often required the craft to go astern or to stop suddenly and rise or descend vertically for a few feet. The trim was tender; a plate of stew and a cup of coffee passed from aft to forward could cause a bow-down angle. First Lieutenants came from a chosen race; no one-man band approached their performance.
Navigation looked crude. In fact, however, it had to be extremely accurate even though the instruments were basic. It was quite usual to go deep, after taking a careful fix, several hundred yards from a narrow gap, perhaps a hundred yards or less across, in the harbor wall; make due allowance for the conflicting currents often present, and only come shallow to fix again when well inside the harbor, zigging while deep to avoid buoy moorings and other obstacles. These efforts were not always successful, but X-Craft were strongly built: dents and scratches resulting from miscalculations were tolerantly ignored and ironed out by a patient dockyard. No special chart was ever designed for X-Craft. The Captain had to fold his regular chart into a suitable size. There was no space for an adequate chart table and no automatic dead reckoning plotter. The chart soon became wet with condensation and the compass rose always seemed to be on the wrong fold. The most important navigational instruments were the Captain’s stop-watch and the gyro; the log was misleading at the slow speeds used during an approach and reliance was placed on carefully timed shaft revolutions instead. Commanding officers soon learned the mental aids to navigation and could estimate their position within yards and sometimes, when close to a target, within feet without recourse to manual plotting.
The simplest way to illustrate tactics and the way in which equipment was used is to describe the sort of incidents which occurred during attacks on defended anchorages and harbors.
The towing submarine and its tow used to surface at night when still well clear of the operational area, transferring the operational crew, rather perilously, in a rubber dinghy. The passage crew returned thankfully to the parent submarine which then submerged and retired to seaward to await a prearranged rendezvous after the operation. Modern techniques—particularly a development of the small rescue submarine concept—could readily enable a midget submarine to be carried on the back of its parent with a connecting hatch between the two. There would then be no need to surface when the X-Craft was released or recovered and the passage crew could be dispensed with. The big submarine would not be hampered by the tow and, if nuclear, could make much better speed during the passage to the area.
In the X-Craft, the crew settled themselves into the positions which they would probably occupy for the next 24 hours or more. The Captain stayed on the casing, secured to the induction pipe, while making best speed on the surface under the cover of darkness. By first light it was hoped to be within about ten miles of the objective so that the craft could submerge for the remainder of the approach without undue expenditure of battery power. At this point the induction mast was lowered; all gash ditched; the position fixed as accurately as possible; and the gyro checked against the sun. The Captain then lowered himself through the hatch, pressed the diving klaxon and ordered depth and speed. It was usual to stay deep for as long as possible so that an economical speed of about three knots could be maintained without broaching. This quiet period while deep gave the crew a final opportunity to check and re-check every piece of equipment; and, as always, there was condensation to be mopped up and bilges dried. If it was safe to do so, the craft would probably make use of any natural cover, such as a rocky outcrop near the coast, in order to run the engine briefly—just breaking surface to do so—and so refresh the air before starting the actual attack. The CO2 scrubber and oxygen generator had a strictly limited performance which it was wise to conserve.
When two miles from the first obstacle—- an antisubmarine net made either of heavy wire or thick steel rings supported by a row of buoys—the diver used to struggle into his suit. This was a tiring and awkward performance in the cramped space forward of the periscope and he was usually helped by the Captain and helmsman. At the same time, the electrician went forward into the battery compartment to lie on top of the battery and look out through the net periscope—a stubby affair designed to observe a net at close quarters. There was generally at least one harbor defense craft patrolling close to the net and it had to be assumed that the net itself was under close observation from the shore and from the boom defense vessels who opened and closed the gate for legitimate visitors.
The time of entering the net had to be planned so that the craft would stem the tide. This enabled the Captain to maneuver into and through the net with the least possible disturbance while still maintaining full control of the craft. If the tide changed, the craft was liable to be swept broadside into the barrier—an uncomfortable situation from which it was difficult to extricate oneself. Assuming that the tide was right, the Captain aimed to put the bow into the net at a speed of about one knot and at about 25 feet below the surface. The diver, up until now sitting gloomily on the head in the wet-and-dry compartment, would then resignedly shut the door and, at a sign from the Captain, start to pump water up into the chamber from an internal main ballast tank immediately below so as not to affect the trim. Flooding up was a cold, claustrophobic, and lonely experience. It terminated in a sudden squeeze as the pressure equalized with that outside. Few men learned to enjoy the process.
As soon as he could open the hatch, the diver climbed out into the murky water and took the net-cutting gun—a hydraulic cutter —from its stowage before clambering down the net as far as the keel of the submarine. From this level he started to cut a slit upwards in the net so that the craft gradually pushed its way through, directed by the electrician in the bow. Before making the final cut at the top to release the craft, the diver made sure that he had firm hold of the craft and that he was on the inshore side of the net; he had no wish to be left behind. When the craft was safely through the net, the diver climbed back into the wet-and-dry compartment, shut the hatch, and drained the water down into the ballast tank again. He usually stayed in his dismal cell; a wet diver was unwelcome in the control room and, in any case, he would soon have another task to perform.
The net was not necessarily the only defence to be overcome. There were active and passive sonars, magnetic detection devices, patrol craft, helicopters, and random scare charges to contend with. A well-handled craft, however, that made the best possible use of concealment, lying on the bottom or perhaps in the shadow of mooring buoys and harbor walls when threatened; and showing the tip of its periscope—the size of a man’s thumb—only briefly and occasionally, was very seldom detected even in peacetime exercises when the harbor defenses had been alerted. Returning to periscope depth from deep was probably the most hazardous operation inside a harbor. A small, passive, hand- rotated sonar was provided but it was difficult to search all around quickly with it and almost impossible to judge bearing-movement with certainty. There were many occasions when the first things the Captain saw on raising the periscope were alarmingly close— on one occasion a pair of sea boots belonging to the coxswain of a motor boat filled the lens.
The craft was usually taken deep—below the keel depth of the target—when about 600 yards from the final objective. Speed was reduced steadily so that as soon as the Captain, craning his neck to see out of the upper scuttle, glimpsed the target shadow like a cloud overhead, he could order the motor to be put astern so as to stop the craft directly below the centerline. The craft was then brought very slowly up until it rested, like a fly on the ceiling, against the special antennae which had been raised for the purpose. Sometimes the Captain had to maneuver to a more favorable position and sometimes, when attacking submarines moored alongside their tender for example, he would have to shift position several times in order to bring the whole group of vessels under attack.
If limpets were to be used, two were usually allotted to each target. The limpets were neutrally buoyant but it was hard work for the diver attaching them to the hulls; barnacles and weed often had to be painstakingly scraped away with a knife before the magnetic pads would hold. Side cargoes— the two-ton ground mines—were easier to dispose of. Their fuses were set from inside the craft and they were simply released, by means of a handwheel operated by the Captain, underneath the target.
After the attack, the Captain was understandably anxious to leave as quickly as possible. The risk of detection increased with time and it was said to be uncomfortable to be around when the limpets or cargoes detonated. Sometimes skill—or, more often, luck—enabled the craft to pass out through the same hole in the net as it had used before. But more often the diver again had to climb out and cut a way through. Then there was the long journey out to the rendezvous point; the exchange of recognition signals; the connection of the tow rope; and finally the reappearance of the passage crew. The operation was over.
Naturally, everything did not always go smoothly. The periscopes might flood; the trim pump motor might blow a fuse while trimming underneath the target; a random scare charge might drop on top of the diver while he was working, and the Captain might spill coffee over a vital portion of the chart. In real life, these and many other, accidents were apt to occur at the wrong moment. Nonetheless, the extreme simplicity of the vehicle and its weapon system, combined with the eyeball-and-contact method of attack, proved in war and in peace that the X-Craft could nearly always achieve its objective.
There are plenty of authentic and intriguing accounts of actual wartime exploits that can be read, including those of the German and Japanese navies. This article can only serve as a re-introduction to the art of midget submarining and as a reminder that these very economical little craft were powerful, versatile, and effective. Some navies still have miniature submersibles of various types; this suggests that we should review our own harbor defenses and build a loyal opposition to test and exercise those defenses. There is much that must be learned again, and many ports and harbors are vulnerable to underwater attack.
None would suggest that X-Craft could replace other weapon systems. But they might well succeed where others fail, particularly in carrying antisubmarine warfare to the enemy’s doorstep. Once again X-Craft could prove to be an invaluable addition to the British Fleet, worth inestimably more than their trifling cost in men and material.