 The strangest stories of World War II is the story of sneak craft attack, favored naval weapon of the have not nations. By swimmer, by human torpedo, by midget submarine, explosive boat and torpedo boat, the Axis powers strove with considerable success to whittle down the naval superiority of the Allies. The Allies learned vigilance the hard way to the tune of thousands of tons of warships and merchantmen sunk and damaged. In the Mediterranean alone, at Alexandria, at Suda Bay, Gibraltar and Algiers, Italian sneak craft accounted for 150,000 tons of Allied shipping. The simplest form of sneak attack is the swimmer. Using a tight fitting rubber suit to protect him from the cold and swim fins to increase his striking range, he could reach targets up to five miles. The breathing apparatus developed by the Italians showed great skill and design. The single oxygen bottle allowed the swimmer to work underwater for at least half an hour. Plenty of time to finish his deadly mission. For attacking shipping, their limpet mines and floating charges contained from four to 40 pounds of super explosive. They wrecked an Imagan bridge by guiding 1,500 pound charges down the river. And throughout the war, they successfully blew up locks along the inland waterways. In attacking ships, the swimmer almost always approached the targets on the surface, relying on his head net to camouflage his face from the lookouts. On reaching it, he put on his nose clip and his mouthpiece for underwater breathing, filled along with oxygen and submerged quietly to the bilge keel. The charge was pulled down after him and clamped to the side of the hull. The time fuse with its four-hour delay was started and the attack was done. Score for the swimmers, the Imagan bridge, many canal locks, but only a few allied ships. The most successful Italian sneak craft was their version of the human torpedo, the Celerolente Corso, the SLC. Popular opinion to the contrary, the SLC was not a suicide craft. It was a modification of a standard torpedo that carried two men and two heavy charges to the target. The two 280 pound warheads were in turn clamped on to the nose of the torpedo for delivery and were readily detachable at the scene of action. One of them was easily capable of breaking the back of a merchant ship. Together they could and did put a capital ship out of commission for a year. The craft was designed to put as little strain as possible on the operator during his long ordeal. Simple airplane type controls for the hydroplanes and rudder. Motor switch with four speeds forward and four reverse. Electric pumps to fill or empty the ballast tanks. The overall length of the SLC was 22 feet and it weighed a little over a ton and a half. The two high pressure bottles carried enough oxygen to last the torpedo men four from five to six hours of continuous use underwater. The captain of the craft sat in the forward position. He handled the controls and did the navigating. Cruising range was 15 miles at a cruising speed of two knots. In December 1941 four of these crafts scored a triumph roughly equivalent to a major sea victory. Slipping into Alexandria Harbor undetected they proved the craft's superior maneuverability and unusual striking power. Each pilot approached within 50 to 60 yards of his target with only his eyes above water. At night detection was almost impossible. Then he submerged and ran slowly and silently to his target. Each craft jockeyed to position under the bilge keel. While the captain held the craft there the number two man ran a line from one bilge keel to the other. Detached the warheads and placed the charges firmly in position directly under the keel. The time clocks were started and they drove away. In this manner two British battleships the Queen Elizabeth and the Valiant and an Allied tanker 80,000 tons of shipping were sunk in Alexandria Harbor in a single night. Later at Gibraltar they were able to bag nine British and American merchantmen. This constant threat of surprise attack was almost as much of a strain on the Allies as the 150,000 tons of shipping actually damaged or sunk. The Germans were inevitably attracted by these spectacular Italian successes and by the spring of 44 it organized a pic core of 10,000 officers and men. Their first successful craft was a one-man human torpedo. The real torpedo, the child, was slung below the mother which carried it to within close firing range of the target. Every detail of the design and operation of martyr was carried out with typical German thoroughness. A welded steel trailer assured rapid delivery at the launching point and camouflage nets preserved the secrecy of the operation. Here was a fairly effective weapon whose mobility was such that it could be quickly concentrated for mass attack. As originally designed the German one-man torpedo was purely a surface craft. Through inexperience the first ones beached harmlessly at Anzio Beach without firing their torpedoes. They were the subject of more curiosity than alarm. But later in the summer of 44 they carried out successful surprise attacks. The low silhouette of the craft running awash with only the dome visible made the run in on a dark night relatively easy. But once he had fired his torpedo and his presence was known he was quite helpless against counter-attack. The Germans could ill afford to sacrifice their trained men and the next craft were made able to dive. Martyr was found to be fully operable at depths up to 90 feet. It handled well and maintained an even course with a speed of a knot and a half is contrasted to a surface speed of somewhat over two knots. Her ability to dive thus immeasurably increased her effectiveness and the sturdy seagoing qualities of the craft underwater exceeded anticipations. The operators even found they could perform radical maneuvers without losing control. However the operator could not see underwater well enough to make an attack. His run into firing range was usually made awash. Even under these conditions visibility was something less than ideal making extremely close range necessary before the torpedo could be fired with any degree of accuracy. 50,000 tons of shipping were thus sunk or damaged in the last year of the war an amount out of all proportion to the martyr losses suffered by the Germans. The development of the midget submarine by the Germans is another chapter in the story of sneak craft attack. First in point of time was Mork, an all-electric one-man midget. She filled the essential requirement of ease and handling by truck to the point of launching and by truck or crane into the water. Mork was not very successful. Her range was a mere 75 miles and she was slow and cumbersome on the surface. Her batteries, which filled the whole forward part of the craft, could drive her at up to four knots. But the swells and anything but the commas seas battered her oversized hydroplanes unmercifully. Yet she had her good points underwater. These same hydroplanes gave the operator excellent control of his craft and she submerged and surfaced with fair success. Under actual operating conditions, she failed to measure up and after two 15-boat sorties in which all craft were lost, she was abandoned. Her successor was the streamlined Bieber, which sacrificed strength for speed. A gas engine was added for surface cruising and recharging the batteries. But her normal range was still restricted to approximately 75 miles. The concavities in the hull permitted the torpedoes to be carried outboard without greatly increasing the bulk of the craft. But they in turn weakened the hull to a considerable degree. Bieber, with her 30-foot overall length and six tons weight, was still small enough to be launched and maintained at quickly constructed strategic points. In her trials, she proved faster and more maneuverable than Mulk. But she was also tricky to handle, hard to navigate and afforded only restricted visibility to the operator. After Mulk was abandoned, Bieber was used constantly against shipping to the port of Antwerp. She had small success and suffered heavy losses. In 15 sorties, using 163 Bieber's, 53 of them, almost a third, failed to return. Bieber was being used as a stop gap until the new midget sub, Zehunt, was ready. Zehunt came into action in December of 44. The German engineers had at last found a small submersible that overcame the annoying limitations of the other craft. Zehunt had the great virtue of being mass produced. She was in essence a trimmed-down model of a full-size submarine and incorporated many of the best features of the British X-Craft, which carried out the raid against the Terpets in her Norwegian fjord the previous year. Her propeller was fitted with the cork nozzle type rudder, similar to that of full-size German submarines. The glass observer's dome on the hatch cover safely withstood water pressure to depths of 150 feet. Her diesel drove her at eight knots on the surface and she handled admirably. Here at last was the best midget submarine German engineering skill could produce. The captain called the orders to the engineer who handled all the controls. He kept her smoothly at periscope depth while he was coached into the target. He made ready for firing and diving. He fired the torpedoes at command and the fish slipped off the track on its run to the target. Tag her down and down they went as the captain took a last quick look through the periscope. Under water, her small size made it almost impossible for the warships to find her. Listening gear was incapable of detecting her propeller noise at slow speed and it was very difficult to ping on her small hull. About 70% of the Zehuins made attacks on allied shipping before the war ended. Though in many cases the crews missed their targets through lack of experience. Through the periscope, they swept the sky for aircraft before surfacing to recharge batteries and for a breath of fresh air. The morale-breaking loneliness of the one-man craft was gone. Zehuint, with her crew of two, could cruise almost 500 miles and stay at sea for a week. But Zehuint came too late and the German defeat prevented her from proving to the skeptical allies that here was a weapon to be reckoned with. In sharp contrast to the successful underwater craft the motorboat story was extremely disappointing to the enemy. The Italians designed a 20-foot torpedo boat, the MTSM, to attack ships either at sea or in the harbors. The propellers were retractable, so the crew of two could easer over a sagging harbor defense net to attack the shipping inside. Two Alpha Romeo engines, one on either side of the single torpedo tube, gave her a top speed of 32 knots. The torpedo was fired by aiming the boat directly at the target. And after firing, the boat was turned sharply away from the following torpedo. This was fine theory that seldom worked out in practice, for the ship's gun crews were able to shoot most of the boats out of the water or drive off the attacks before damage was done. The German version of the torpedo boat was the Wendell boat, a lean, streamlined craft with a single, non-retractable prop. Two torpedoes were shot from the stern and so arranged that one was fired on the run-in and the other was fired during the retreat. In addition, her armament boasted two rocket launchers, one on either side of the pilot house. Like the other sneak craft, she required comparatively calm seas for operations. Her high speed of 33 knots and the two rockets were supposed to disrupt enemy gun crews, so she had a better chance to get within proper torpedo range. The Wendell boat made fine propaganda pictures for the Nazi newsreels, but her performance as an offensive weapon was no more impressive than her Italian counterpart. The explosive boat was a simpler method of delivering a charge to the target. The Italians used it successfully in the last war and continued to experiment during the 1920s and 30s. They developed a hull that planed beautifully into an Alpha Romeo engine that gave speeds up to 30 knots. The combined propeller rudder could be swiveled at will so that with a trained operator at the wheel, the usual type of torpedo net defense could be hurtled with surprising ease. Although in actual operations, the boat was sneaked over the nets as quietly as possible under cover of darkness. In the early years of the war, the Mediterranean was alive with these craft. They swarmed into Malta and Suda Bay in mass attacks, but the ease with which they were spotted and their extreme vulnerability to gunfire placed them in the category of nuisance craft rather than effective offensive ones. Nevertheless, because it was a cheap way of delivering a massive 800-pound charge to its target, the Germans copied the Italian explosive boat. Trailer drawn and usually launched directly from the trailer, the German craft, Linzer, was a much cheaper mass-produced boat with a Ford V8-type engine, non-retractable prop, and indifferent sea-worthiness. In the dying days of the war, the Germans played up Linzer to bolster morale at home. Spectacular pictures of this secret weapon and fake shots of the damage it could do were intended by the Goebbels machine to whip the starving Germans into a frenzy of enthusiasm. The driver aimed his boat like a gun, locked his controls on a collision course, and at the last possible moment jumped. The 800-pound charge detonating on contact supposedly did the rest. Near the end of the war, the Nazis formed a new combat unit to manned radio-controlled explosive boats. The radio-controlled man in the pilot boat steered the other craft and could regulate the speed. Three boats made up a combat team. A pilot boat and two explosive boats. A pilot drove each explosive boat until an attack was started. Then he jumped overboard, and to quote the Germans, he was nearly always rescued, either before or after the operation. Radio control made little difference. It saved the lives of a few Nazi boatmen, but the guns of the escort ships still blasted the boats out of the water with almost 100% success. Against an alert enemy, the motorboat idea in any form was a dismal failure. Too late for this war, but almost ready for operation, were two new craft, one German and one Italian. This is the German High, an attempt at a super one-man human torpedo. Its increased length doubled its battery capacity, which could be used for increased range, faster speed, or both. But its great length, over 40 feet, made it extraordinarily clumsy and an ever-present potential death trap for the operator. High failed, and the German unconditional surrender stopped further experiments. Directly opposite to the German High was the Italian SSB, which was also caught by the war's ending before she could get into action. Except for the midget submarine, Zehun, she was probably the finest sneak craft to come out of the war. Her two enormous warheads total nearly 900 pounds of high explosive. The crew of two rides inside a cockpit, which protects them from the water pressure and helps streamline the craft. The face masks and breathing gear are the same as on the older two-man torpedo and can be put on even after the men are underwater. SSB is 26 feet long, weighs a little over two tons, and has a top speed of six knots. Whether turning, diving, or running, the control is positive and rapid. Look at the ease with which the pilot dives and climbs underwater. The SSB is fast and powerful enough to overcome many of the tides and currents that prevented the other two-man and one-man torpedoes from operating successfully. And her cruising range of 45 miles is three times as great as that of the older model. Watch the fast, sharp turn to the left as she surfaces. Shipping is attacked in the same manner as with the older two-man torpedo. For operative technique, the whole operation is shown on the surface beside a ship. After coming alongside submerged and in a real operation, sinking to the bilge keel, the number two man gets out of the craft with his clamps and fastens them to the bilge keel. As this is a merchant ship of 6,000 tons, only one warhead is needed to blow a tremendous hole, break her back, and sink her. The clamp holding the first section of the head is loosened. While this is being done, the captain holds his craft in position under the bilge keel in a real operation alongside the ship in this demonstration. When the head is loose, a twist or two by the man underwater frees it from the craft. As it has only two pounds of positive buoyancy, it is easy to pull it under and fasten it to the hull. The number two man then climbs back aboard his craft. With the second section of the warhead still in place, the SSB can attack another ship, making it possible for two men to sink two ships in one operation. This was the array of sneak craft pitted against the Allies, and the Allies learned by hard lessons that the best defense against them was constant vigilance and a full dress harbor defense. Attacking a harbor, the sneak craft could easily evade the long range surface search radar or deep water magnetic loops at the harbor mouth. Even the line of sonoboys on the surface or hydrophones on the bottom could seldom pick up their weak propeller beats, and then only if the craft were operating at high speed. The long range heralds set up on either side of the harbor will not detect sneak craft. They are for the full size submarines and surface vessels. One possible means of detection is the multi-turn loop, which in some cases will record the passage of the midget craft. Another detection possibility is the short pulse herald. This device can ping on a very small object, but requires constant alertness, the most expert of operators, and ideal sound and hydrographic conditions. The surface of this water is swept by super sensitive radar that picks up objects as small as a periscope or a perspex dome or a swimmer's head. Radio in the harbor entrance control post directs the cutters to the attack. Torpedo nets are the last line of fixed defense. The latest and best stopped torpedoes, one-man human torpedoes, midget subs, and with specially rigged surface elements, they stop motorboats. The two-man torpedoes and the swimmers were the only ones who could make their way past the net defenses, using net cutters or slipping through openings near the shore. The harbor patrol boats armed with search lights, machine guns, and depth charges were constantly searching for the sneak attackers who were able to penetrate these defenses. At slow speeds, these underwater craft made little or no noise with their propellers or engines, sometimes at a very close range and under the very best of listening conditions, a skillful operator might faintly hear the propeller beats. Of course, if the craft makes a maneuver such as this crash dive of the Zehuint, the experienced sound operator could quite easily hear it. However, exhaustive tests have proved that under sneak attack conditions, it is next to impossible to hear any of these midget craft. The electric torpedo is by no means silent. True, the sound operator hears it the instant it is fired, but then it is much too late. The latest detection devices developed at the end of the war but not yet installed in our harbors were the multi-turn loop and the short pulse herald. The multi-turn loop in 60 feet of water is the most sensitive of magnetic detection instruments. However, a sneak craft built of non-magnetic material should be able to cross such a loop without detection. The short pulse herald promised to be one of the most effective detection devices in use. Tests revealed that up to 400 yards, this device with skillful operation could detect sneak craft under average condition. These and the radar were the newest weapons for harbor defense. The end of the war found the sneak craft that had been so crudely and hastily built for defense about to become important secret weapons of offense. It needs but little imagination to see what these craft could do to even our largest shore installations, should they be equipped with new atomic weapons. To be secure is to keep well-abressed of all future improvements in sneak weapons and to press vigorously the development of more dependable detection equipment and countermeasures so that we may not be caught by this form of the opening gun of modern warfare, the sneak attack.