The Insane Explosive Motorboats of WWII

In the early morning hours of March 26, 1941, Royal Navy sailors on watch at Souda Bay, on the northern coast of Crete, were alarmed by an unusual sound: the high-pitched whine of high-powered engines, growing ever louder. As the sailors strained their eyes into the pre-dawn gloom, a swarm of tiny, fast-moving craft suddenly burst from the darkness, heading straight for them. There was no time to react; within seconds, large explosions shook four ships – including the heavy cruiser HMS York and the Norwegian tanker Pericles – sending up tall geysers of flame and water. Believing the fleet was under air attack, antiaircraft guns aboard British warships opened fire, sending tracers dancing into the night sky. But the attackers were already gone. When dawn finally broke over Souda Bay, four ships lay at the bottom and dozens of sailors dead. The Royal Navy had fallen victim to the Italian Regia Marina’s secret weapon: the Motoscafa da Turismo or MT, a high-speed motorboat packed with high explosives whose daring pilots had to jump free just before impact to avoid certain death. By the time the Second World War ended in August 1945, two other Axis powers – Nazi Germany and Imperial Japan – would also deploy similar craft – with widely varying results. This is the story of one of WWII’s most bizarre naval weapons.

The Italian Navy was a pioneer in the development of naval special forces. During the First World War, Italian naval engineer Raffaele Rossetti invented an innovative new weapon called the mignatta or “leech”. This was effectively a low-speed electric torpedo fitted with a detachable explosive warhead and handles for two combat swimmers to cling to the side. Riding the mignatta with their heads just above the water, the swimmers would infiltrate an enemy harbour, attach the warhead to the hull of a target ship, and set a time fuse. They would then escape before the warhead detonated. On November 1, 1918, Rossetti, along with Raffaele Paolucci, used the mignatta to attack the Austrian battleship Viribis Unitis, anchored in Pula Bay in what is now Croatia. While the two swimmers were immediately captured, the crew of the battleship did not believe their story and re-boarded the ship, which immediately sank and capsized killing 400 sailors. Unbeknownst to the Italians, just a few hours before the attack the ship had been transferred over to the newly-created State of Slovenes, Croats, and Serbs – officially allied with Italy – and renamed the Jugoslavija.

Two decades later in 1941, the Italian Navy created a dedicated special forces unit called the Decima Flottiglia Motoscafi Armati Silurianti or “10th Assault Vehicle Flotilla” – better known as the Decima MAS. Assembled and commanded by aristocrat Captain Junio Valerio Borghese – AKA the “Black Prince”, the Decima developed a number of innovative weapons including the Silurio Lenta Corsa or “Low-Speed Torpedo” – better known as the maiale or “pig.” Effectively an upgraded version of the earlier mignatta, the maiale was an electrically-driven torpedo with a detachable warhead designed to be ridden into enemy harbours by a pair of combat frogmen – this time equipped with underwater breathing apparatus. Using maiale, the men of the Decima carried out a number of daring and successful raids on British harbours in the Mediterranean, including Alexandria and Gibraltar. These operations, in turn, inspired the British to create their own combat frogmen, manned torpedoes, and midget submarines.

Another weapon developed by the Decima was the Motoscafa da Turismo or “high-speed motor boat”, nicknamed the barchino or “little boat.” This was a 5.6 metre long wooden motor boat with a canvas deck, powered by a 95 horsepower Alfa Romeo outboard motor that gave it a top speed of 33 knots or 61 kilometres per hour. The bow was packed with 300 kilograms of high explosive, while the single pilot rode in a small cockpit overhanging the rear transom. Barchini were designed to be carried close to their targets by a mothership, whereupon they would be launched and infiltrate an enemy harbour at low speed to avoid detection. When within around 100-200 metres of the target, the pilot would lock the rudder, open the throttle, and pull an escape handle, which would engage a primitive ejection seat and launch him overboard. The barchino would continue forward at full speed until it impacted the target’s hull. This detonated a small explosive charge that ripped off the boat’s bow and caused the boat to sink, whereupon a hydrostatic fuze would detonate the main charge at a depth of one metre. If the pilot was lucky, he would be picked up by the mother ship and returned to base.

The MTs were built by the companies Baglietto of Varazze and CABI of Milan, with the first examples being delivered for testing in early 1939. Test attacks against the obsolete cruiser Quarto revealed numerous flaws, such as a lack of adequate engine power and a tendency for the hull to leak at high speeds. This led to the development of the faster and more seaworthy Motoscafo da Turismo Modificato or MTM, which entered service in November 1940. The MTMs were first used operationally in the March 26, 1941 raid on Souda Bay in Crete, for which the boats were ferried to their targets by the destroyers Franscesco Crispi and Quintino Sella. The raid resulted in four ships sunk and all six barchino pilots being captured by the British. But while both HMS York and the Pericles sank in shallow water and were soon re-floated, the former was scuttled by its crew when the Germans invaded Crete in May 1942, while the latter sank under tow in April while under tow to Alexandria.

On the 26th of July, 1941, the Decima launched an attack against Grand Harbour in Valetta, Malta using two maiale human torpedoes and six barchini. Unfortunately, the mission was a complete failure, the British having detected the raiders as they were being launched. All eight vehicles were destroyed, fifteen Italians killed, and eighteen captured. The only damage inflicted was to a bridge linking the breakwater to Fort St. Elmo, which was struck by a barchino and destroyed. In the wake of this disaster, the Italians would attempt to use barchini on a number of different occasions, including along the Egyptian-Libyan coast and in the Black Sea in support of the German invasion of Russia. However, none of these operations were very successful. Following the signing of the Italian armistice with the Allies in September 1943, the Italian Social Republic, the fascist puppet state in Northern Italy, continued to build and use barchini in combat. One of the last victories scored by the strange vehicles was against the French destroyer Trombe, which was heavily damaged off the northern Italian coast on April 16, 1945 – three weeks before the end of the war. After the war, four MTMs were captured and used by Shayetet 13, the naval commandoes of what would soon become the state of Israel. On October 22, 1948, during the Israeli War of Independence, the boats were used to attack the Egyptian sloop El Emir Farouq. The sloop sank in five minutes, while a nearby minesweeper was heavily damaged.

Explosive motor boats were also deployed by Nazi Germany. As covered in our previous video The Laughably Awful German Midget Submarines, by mid-1944 the effectiveness of the German Kriegsmarine had been all but neutralized. Advancements in Allied anti-submarine technology and tactics had put the once-mighty U-boat arm permanently on the back foot, while the German surface fleet – never large to begin with – remained largely bottled up in port, the German High Command hesitant to risk its expensive capital ships in combat. And with the Allies having established solid beachheads in Normandy and Southern France, the Kriegsmarine was desperate for new ways to strike back at the seemingly unstoppable tide of Allied shipping. And so it was that in late 1943, Admiral Karl Dönitz, head of the U-boat arm, established an elite naval attack unit under the command of Rear Admiral Hellmuth Heye. Though officially known as Marine Einsatz Abteilung or “Special Naval Attack Force”, these forces were colloquially known as Klein Kampf Verbände, K-Verbände, or simply “K-units”. The K-Verbände fielded a number of strange weapons, including a series of midget submarines such as the Neger, Seehund, and Biber. They also developed their own explosive motor boats known as the linsen or “lentils.” The dimensions, performance, and mission profile of the linsen were very similar to the Italian barchini, but with one major difference: linsen could be guided remotely by radio, allowing attacks to be carried out from greater distances. However, the boats still needed human pilots to guide them close to their targets. Once in position, the pilot turned on the radio receiver, opened the throttle, and jumped free. Meanwhile, a radio operator aboard an accompanying command boat guided the linse towards its target, using a set of red and green lights to maintain alignment. If all went well – and that was a big if – the pilot would then be rescued by the command boat and returned to base. Linsen were organized into attack groups called rotten, comprising two attack boats and one command boat. Four rotten made up a gruppe, while four gruppe made up a flotilla.

Linsen were first used on the night of August 2, 1944. Along with 58 Neger human torpedoes, 32 Linsen carried out an attack against Allied shipping off the coast of Normandy. The mission was a complete failure, with 41 Linsen and Neger being destroyed for the loss of zero Allied vessels. Several more attacks were carried out in Normandy and the Belgian port of Antwerp – with similar results. In total, the Linsen flotillas claimed only eight enemy ships sunk, including one cruiser, two destroyers, and two freighters. Meanwhile, nearly 70 boats and their crews were lost. One of the main shortcomings of the Linsen was their relatively low speed, which made them vulnerable to enemy fire. In response, German naval engineers set out to develop a faster version known as the Tornado. This was effectively a pair of surplus seaplane floats held together by a simple frame and powered by the same Argus 109-014 pulse-jet engine used on the infamous V-1 flying bomb. While theoretically much faster than the Linse, the Tornado was doomed by the unavailability of 109-014 engines, which were all earmarked for V-1 production. Another proposed alternative was the Schlitten or “Sledge”, an upgraded Linsen fitted with a Ford V8 engine that gave it a top speed of 65 knots. However, the war ended before this craft could see combat.

As a side note, just like with the Italians with human torpedoes, the German use of remote-controlled explosive speedboats actually goes back to the First World War. In the final years of the conflict, the German Imperial Navy fielded an advanced weapon called the Fernlenkboot or FL-boot- a 17-metre-long speedboat packed with 700 kilograms of explosives which had a top speed of 30 knots and was guided from the shore through a spool of wire 20 kilometres long. The devices were used against British shipping off the coast of Flanders, with one successfully sinking the Royal Navy monitor HMS Erebus on March 1, 1917. It was among the first successful uses of an unmanned vehicle or “drone” in military history.

It is perhaps unsurprising that Imperial Japan also used explosive motor boats during WWII. However, unlike their Italian and German counterparts the Japanese pilots made no attempt to bail out prior to impact, using their craft – known as Shinyo or “Sea Quake” as suicide weapons in the Kamikaze tradition. Shinyo were developed starting in March of 1944, with the first examples being based on regular 18-metre steel-hulled torpedo boats. Construction, however, was quickly switched over to wood due to a shortage of raw materials. Driven by one pilot, unarmed the vessels had a top speed of 23 knots. However, when fitted with a 270 kilogram explosive charge, this dropped to only 18 knots, making the Shinyo extremely vulnerable to enemy fire. Consequently, many vessels were also fitted with a pair of 120mm anti-ship rockets for self-defence. A similar vessel known as the Maru-Ni was also developed for the Japanese Imperial Army, which was armed with two depth charges. Unlike the Shinyo, Maru-Ni were not intended to be suicide craft; instead, the pilot was expected to drop his depth charges, turn around, and speed away before the weapons exploded. However, the blast radius of the charges made survival practically impossible.

On August 1, 1944, 400 students reported for Shinyo training at the Naval Torpedo School at Kawatana near Yokosuka. Nearly all were Air Force or Navy Kamikaze pilots, who had transferred over due to a shortage of aircraft. The students, whose average age was 17, were given three choices of assignment: conventional torpedo boats, Shinyo suicide boats, or as suicide frogmen or Fukuryu. Around 150 students chose Shinyo duty. 6,197 Shinyo were produced by war’s end, with 1,100 being deployed to the Philippines, 400 to Okinawa and Formosa – today Taiwan – and smaller numbers to Korea, Shanghai, Hong Kong, Hainan, and Singapore. The vast majority, however, were deployed along the Japanese coast in preparation for the anticipated Allied invasion.

The Shinyo managed to score a handful of victories, most notably the sinking of the Landing Craft Infantry LCI(G)-365 and LCI(M)-974 near the Philippines and the damaging of the destroyers USS Charles J Badger and USS Hutchins off Okinawa. However, due to their slow speed, the vast majority of the craft were picked off by Allied guns before they could get anywhere near their targets. Just like the Italian Barchini and German Linsen, the Shinyo was a weapon of last resort, deployed in desperation by a fighting force whose fate was already sealed.

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