The Tirpitz’s base at Kaafjord was 1,000 miles from the closest air base in Britain but only 50 miles from route used by the Artic convoys. The entrance to the fjord was protected by anti-submarine nets and was lit every night by floodlights. The outer fjord was also protected by anti-submarine nets and guarded by patrol boats and shore batteries. Anti-aircraft batteries ringed the tops of the cliffs, troops patrolled to ensure that Norwegian saboteurs could not reach the ship and there was enough smoke screen equipment to cover the entire fjord. No wonder the admiral in charge could relax once the ship was safe in her cocoon.

However, he would not have been so complacent if he knew that Royal Navy engineers had been working for the past three years to develop a new type of submarine, smaller and more flexible than traditional submarines but with a much greater range than already existing midget submarines. The defenses at Kaafjord were designed against a traditional submarine but a midget submarine could fool a radar operator into thinking that it was a large fish or school of herring and thus sneak in.

The actual prototype was built by a private company, Varley Marine Limited, and it was launched on March 19, 1942. While the engineers wrestled with the technical problems, the navy was screening volunteers without actually telling them what they were volunteering for other than that they needed to be good swimmers. Those who passed were divided into two groups, divers and operators, and sent to the huge submarine base at Portsmouth, where they trained separately and did not even know of each other’s existence.

The divers spent every day in the water in order to build up their endurance until they could spend six hours at a time working underwater. The operators were given basic underwater training as well but mainly focused on becoming familiar with the operation of a midget submarine they had never seen.  

The men drilled and drilled while constantly training in order to become as lean as possible. Once they had worked out all of the bugs of the original prototype, Vickers Armstrong Limited was told to make six X-craft. After their training was completed, the men were given two weeks leave and then sent to a hotel near the sea in Scotland, which had been taken over by the British Admiralty. Given the importance of the mission, the men were surprised by the total lack of security. Tourists were still allowed to walk along the waterfront, which seems strange, but guards and barbed wire fences would have attracted attention. The men handled any questions from locals or tourists by simply saying that they were testing rough water motorboats.

While the men trained endlessly, the planners in the Admiralty considered how to best transport the X-Craft within range of the fjord and consulted with Norwegian sailors and fishermen to map out the tides, currents and depths of the channels leading to the fjord. Aircrew were sent to the Russian airfield near Murmansk, Vaenga, and they made regular reconnaissance runs over the Tirpitz. However, up-to-date information about the routines and level of vigilance of the Tirpitz’s crew was crucial. Fortunately, the Norwegian Resistance was made up of brave, resourceful people, who proved able to supply the British Navy with priceless information.

The six operational X-Craft (X-5 to X-10) arrived during January 1943. The majority of standard submarine equipment would not fit in an X-Craft and there was not enough time to custom design equipment for the midget submarines, so the engineers had improvised. A regular fan motor propelled the craft underwater and the same bus engines used by double-deckers powered the X-Craft underwater. There was certainly not enough time to make the insides comfortable, instead the total internal space of thirty-five feet was divided into four compartments, only one of which could hold all four crewmen at one time, and each compartment was packed with equipment, pumps, valves and pipes, so there was no space where a man could stretch out and rest properly. The midget submarines could do most of the things that a regular sub could, it could dive as deep, but its speed was slower, two knots below surface and six knots above surface. Unlike a standard submarine, the X-craft had glass viewing ports above and flanking the captain’s command position. Its only weapons were a pair of two-ton explosive charges that were placed on the port and starboard sides. The explosives were designed to stay in place once they were released instead of rising to the surface. The forward compartment was designed to allow the diver to go into the water and cut through the anti-submarine nets.

The Admiralty eventually decided that the only way to avoid detection was to have six regular submarines tow the X-craft underwater to the target area and a backup crew would man the midget submarines during the crossing while the main crews rested in the submarines.

The crews knew their craft inside out because each crew was sent to the Vickers Armstrong yards to observe how their specific craft was put together. This was vital since there were so many things that could go wrong with the equipment and the four men would have to make any repairs themselves.  

The mission had originally been planned for the spring of 1943 to take advantage of the last of the artic darkness but the backup crews needed to be trained so the mission was postponed to the fall, which gave all of the crews more time to train.

Partway through the crossing, the crews were notified that X-5, X-6 and X-7 would attack the Tirpitz, X-9 and X-10 the battleship Scharnhorst and X-8 the pocket battleship Lutzow.

The passage crews spent six days in the X-craft during the crossing, surfacing every six hours for only 15 minutes to recycle the air. With a crew of only three men, there was no opportunity to rest, so they were issued Benzedrine to stay alert. Even though they were all hardened sailors, the men would be throwing up constantly whenever the craft entered rough seas, but they had to keep working and clean up the mess otherwise the condensation produced by their sweat would cause short circuits.

X-8’s tow cable snapped during the fifth day and it took a day and half before it was found but the passage crew was so exhausted that the operational crew took over early.   X-7’s tow line also snapped but an alert sailor on the submarine noticed it immediately and the line was reattached although not without considerable risk and effort. X-9’s tow cable parted as well but it sank before it could be found. Perhaps a tougher tow line would have been a worthwhile investment because the three craft that had the new nylon towing lines had no problems, only the old manila lines snapped. X-8 later had a problem with one of its explosive charges and although the charge was dropped far behind with a two hour time delay, the explosion still caused enough damage that it was unable to complete the mission, so it was scuttled.

The four remaining X-craft carried out their crew transfers on the evening of September 19 and began their approaches the next evening. However, mechanical problems forced X-10 to return to her parent submarine, so only the Tirpitz would be attacked. The fjord’s defenses proved tricky to get past and it took X-6 until the evening of September 21 to reach four miles from Kaafjord. Actually, all three X-craft were only a few hundred yards from each other by that time but none could see the other, so each crew spent a nervous night waiting for the morning when they would attempt to get through the antisubmarine net three miles away from the Tirptiz. The crews had been given specific times when they could release their charges in order to avoid them putting the other crews in danger and the firing clocks for the charges were supposed to be set to six hours to give the crews time to get away safely.

The diver left X-6 early in the morning of September 22. The diver had to cut the net strand by strand until the craft could go through at a speed of one knot and then he would have to walk with the loose strands to the end of the craft to ensure that they did not become tangled in the propeller before making sure that he grabbed the rung at the end so that he was not left behind and then re-enter. However, the commander of the X-6 knew that he had a faulty periscope so he took the risk of surfacing and following a trawler through the surface gate and fortunately for them, no one noticed. The craft then made its way slowly and carefully to the Tirpitz.

Since the Tirpitz’s antisubmarine nets were only 50 feet long in water that was 120 feet deep, they expected to simply go under the nets, so they were shocked to find that the Germans had developed a series of three overlapping nets that did go all the way to the bottom. The craft made it through by using a boat gate meant for shallow boats, the Germans did not think that any enemy craft could get this close unseen. X-6 rose too quickly at one point and was noticed by an alert petty officer but the crew had been worn out by the endless drills and fake alarms so no one believed him, instead they thought it was just another test. As a result, it took thirteen minutes before anyone did anything, by which time the craft was directly under the ship’s heel. German sailors were shooting at them with rifles, which could not penetrate the hull, so the crew released their bombs at 0722 with a time delay of one hour. Unknown to them, X-7 had released its charges 12 minutes earlier and X-5 was still two miles away.

Knowing they would have to scuttle their craft, the crew of X-6 quickly destroyed all secret documents before shooting up to the surface and surrendering. While they were being transported to the ship, their craft slowly sank to the bottom. All they would tell the Germans was that they were British. The captain knew that the Tirpitz was in danger but it would take too long to get the ship moving. While the captain debated his options, X-7 had become entangled in the ship’s nets and it only escaped by shooting up to the surface where it was seen and fired at before immediately sinking again. The two senior crew members of X-6 were being interrogated when the bombs went off at 0812, the first two setting off the other two. X-7 was captured roughly 20 minutes after the explosion but only two of the crew made it out in time. X-5 surfaced a few minutes after X-7 but it was within range of the Tirpitz’s 4-inch guns and was immediately blown out of the water.

Documents taken from X-7 showed how well prepared the attack had been and the wealth of details about the ship’s routine made it clear that the Norwegian Resistance had been more effective than thought, which sparked a vicious campaign by the Gestapo that still failed to make serious inroads into the resistance.

Although the Tirptiz was not sunk, the damage was serious enough to put it out of action until the following spring. However, the Admiralty would not rest until the Tirpitz was eliminated for once and for all, so more men would lose their lives in further attempts to sink the Beast .

Related Movies:

Submarine X-1 (1968)
Directed by William Graham, starring James Caan and David Sumner
Midget submarines try to destroy Germany's most powerful warship during WWII. (please click here to read the review)
 
Further Reading:

The X-Craft Raid-Thomas Gallagher, New York: Harcourt Brace Jovanovich, Inc, 1971

It is a good book with solid research that details the grueling training, as well as the dangerous risks faced by the members of the Norwegian Resistance who provided the British Navy with information about the Tirpitz’s routine. A picture of the only surviving X-craft and a model of the interior of the craft show just how cramped and unbearable it would have been for six days straight. However, it is not an exciting read and is really meant for specialists in the field.

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